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Regulation of the High Affinity Receptor for IgE on Human Epidermal Langerhans Cells¹

Stefan Kraft^*, Jörg H. M. Weßendorf^*, Daniel Hanau and Thomas Bieber^2,*

^* Department of Dermatology, Friedrich Wilhelms University, Bonn, Germany; and Laboratoire d’Histocompatibilité, Etablissement Régional de Transfusion Sanguine, Strasbourg, France

	Abstract

Top Abstract Introduction Materials and Methods Results Discussion References

 
Human epidermal Langerhans cells (LC) express variable amounts of the high affinity receptor for IgE (FcRI); the strongest expression is characteristic of atopic dermatitis. The receptor is suggested to take part in the pathophysiology of this disease by acting as a link between aeroallergens and Ag-specific T cells in an IgE-mediated, delayed-type hypersensitivity reaction. In the present study we show that even in the absence of surface expression, normal LC maintain an intracellular pool of the -chain of FcRI (FcRI) of the same m.w. as the surface-bound FcRI that is able to bind significant amounts of IgE. The lack of surface expression is linked to the absence or very low expression of the -chain (FcRI). Moreover, the amount of FcRI expressed at the cell surface significantly correlates with the amount of FcRI. LC differentiation toward lymphoid dendritic cells is accompanied by the disappearance of transcripts for FcRI, but not for FcRI. This leads to a rapid decrease in the intracellular and surface levels of FcRI, which cannot be influenced by IL-4, IgE, or other agents. Overall, our findings suggest that these mechanisms enable LC to be highly versatile APCs by rapidly adapting the surface level of FcRI to distinct inflammatory environments.

	Introduction

Top Abstract Introduction Materials and Methods Results Discussion References

 
The high affinity receptor for IgE (FcRI)³ belongs to the family of so-called multichain immune recognition receptors (1) that includes the TCR, the B cell receptor, and receptors for the Fc fragments of IgG (FcR). FcRI has been shown to be expressed on two distinct groups of cells: 1) on effector cells of anaphylaxis and allergy, i.e., on mast cells, basophils, and eosinophils (2, 3, 4); and 2) on professional APCs, including Langerhans cells (LC) (5, 6), monocytes (7), circulating dendritic cells (DC) (8), as well as inflammatory dendritic epidermal cells (EC) (9). LC serve as an outpost of the immune system in the skin (and other interface epithelia in the lung, gastrointestinal tract, and nasal mucosa), continuously informing it about the invasion of pathogens or allergens (10). We previously reported that FcRI is not constitutively expressed on human epidermal LC, unlike on effector cells of anaphylaxis, but displays a large variation of expression density (9, 11, 12, 13). Most interestingly, the strongest up-regulation of FcRI expression is specifically observed on LC and related DC in lesional skin of patients with atopic dermatitis (AD) and correlates to the IgE serum level (9, 14). There is also evidence that LC from atopic skin use IgE for Ag presentation (15), and that FcRI is the structure used for allergen uptake by monocytes (16) and peripheral blood DC (8). Furthermore, only LC from atopic individuals expressing high amounts of FcRI are fully activated upon receptor ligation (12, 13). These and other findings suggest a role for this structure on LC as the crucial link between aeroallergens and Ag-specific T cells in a delayed-type hypersensitivity reaction (reviewed in Refs. 17–19). With regard to these profound functional consequences, the characterization of the mechanisms regulating FcRI expression on human LC is of major interest.

	Materials and Methods

Top Abstract Introduction Materials and Methods Results Discussion References

 
Reagents

Anti-CD16 mAb 3G8 (IgG1) was obtained from Immunotech (Marseille, France). Phycoerythrin (PE)-labeled T6/RD1 (IgG1; Coultertronics, Krefeld, Germany) and unlabeled IOT6 mAb (IgG1; Immunotech) are directed against CD1a, which is present in the epidermis only on LC (20). The mAbs 22E7 (IgG1) and 4D8 (IgG2b; gifts from Dr. J. Kochan, Department of Autoimmune Diseases, Hoffmann-La Roche, Nutley, NJ) react with the and subunits of FcRI, respectively (21, 22). RAB1 was a gift from Dr. Torbjörn Bjerke (Aarhus, Denmark) and is a polyclonal Ab specific for human FcRI generated in rabbits by injecting purified soluble FcRI expressed in Chinese hamster ovarian cells. Human myeloma IgE (PS) was obtained from Calbiochem (Bad Soden, Germany). FITC-labeled anti-human IgE mAb was purchased from Nordic Immunology (Tilburg, The Netherlands). FITC-labeled F(ab')₂ of goat anti-mouse Ab (GaM/FITC) was purchased from Jackson ImmunoResearch Laboratories (West Grove, PA). Unlabeled and PE-labeled IgG1 were obtained from Becton Dickinson (Mountain View, CA). Oligonucleotides were synthesized by MWG Biotech (Ebersberg, Germany). Sheep anti-mouse coated magnetic beads (M-280) were obtained from Dynal (Oslo, Norway). Peroxidase-conjugated goat anti-mouse Ig Ab was obtained from Bio-Rad (Richmond, CA). Peroxidase-conjugated goat anti-rabbit Ig Ab, DNase (D-4263), digitonin (D-1407), and saponin (S-7900) were purchased from Sigma (St. Louis, MO). RPMI 1640 medium was obtained from Biochrom (Berlin, Germany). FCS, L-glutamine, and antibiotics/antimycotics were purchased from Life Technologies (Eggenstein, Germany).

Cell lines

The cell lines U937 and Jurkat E6.1 were obtained from the American Tissue Culture Collection (Rockville, MD). The endothelial cell line ECV304 was obtained from Dr. Thomas Maciag (American Red Cross, Rockville, MD). RBL-48 cells were obtained by transfecting the gene coding for human FcRI into RBL-2H3 cells (23) and were a gift from Dr. J. Kochan (Nutley, NJ).

Preparation and culture of LC-enriched EC suspensions

Split-thickness skin specimens from normal appearing skin were obtained from our surgery department and from chronic, untreated (at least 3 wk) lesional skin of patients with AD. Written informed consent was obtained from all the patients and volunteers. Crude EC suspensions were obtained as follows. The skin samples were cut into pieces of about 3 to 4 mm x 10 to 20 mm and incubated with 0.5% trypsin in PBS at 37°C for 90 to 120 min. Then the epidermal sheets were removed with a fine forceps and stirred for 10 min in washing medium (containing RPMI 1640, 10% FCS, 1% L-glutamine, and 1% antibiotics/antimycotics) with additional DNase in a final concentration of 0.01% to yield an EC suspension, which was filtrated through a sterile gauze swab. Enrichment of LC was performed as described in detail previously (24). Briefly, EC suspensions were subjected to density gradient centrifugation (density = 1.077; Lymphoprep, Nyegaard, Oslo, Norway). The interface cell layer was then collected, washed, and resuspended in washing medium, and the enrichment for LC (20–50%) was controlled by T6/RD1 immunolabeling. The entire procedure takes about 10 h, and the final cell preparation is referred to as LC-enriched EC. Spontaneously emigrating LC were prepared as described previously (25). A possible contamination of the cell samples by CD1a-negative cells expressing FcRI, i.e., basophils, mast cells, eosinophils, or monocytes, was excluded by double immunolabeling and flow cytometry as previously described (5).

EC were cultured (1 x 10⁶ cells/ml) for up to 36 h as previously described (13). In some experiments, recombinant human granulocyte-macrophage CSF (GM-CSF; 500 IU/ml), TNF- (100 IU/ml), IL-4 (250 IU/ml), IFN- (250 IU/ml; all from Genzyme, Boston, MA), and TGF-ß (10 ng/ml; Becton Dickinson) were added for up to 36 h.

Preparation of purified LC and LC-depleted EC

Crude EC suspensions were prepared as described above. Then, EC were purified by positive selection with an anti-CD1a mAb bound to magnetic beads according to the manufacturer’s protocol. Briefly, Dynabeads M-280 precoated with sheep anti-mouse Ab were incubated with the anti-CD1a mAb IOT6. After a washing step, crude EC suspensions were added to the bead suspensions and incubated for 1 h at 4°C. CD1a-positive cells bound to the beads were then purified by performing several washing steps with the magnet. The purity of the LC preparation was controlled after each application to the magnet by light microscopy, and the procedure was stopped when unbound cells were completely removed. Usually, at least 8 to 10 applications and washes were necessary to yield a highly purified LC (>98%) preparation. These cells are referred to as purified LC. LC-depleted EC were obtained by negative selection using the same method.

Flow cytometric analysis of surface and intracellular expression of FcRI subunits and IgE-binding studies on epidermal Langerhans cells

EC (5 x 10⁵) were chilled on ice and washed several times with cold PBS supplemented with 1% FCS and 0.1% sodium azide. Double-staining experiments for the detection of surface or intracellular distribution of FcRI subunits were performed as described in detail previously (5, 9, 26). Briefly, for determination of intracellular FcRI expression, up to 500,000 EC were washed twice in PBS, fixed in PBS and 4% formaldehyde for 20 min, washed in PBS, incubated in PBS and 0.1 M glycine for 10 min, washed in PBS twice, and permeabilized in PBS, 0.5% saponin, 0.5% BSA, 0.01% sodium azide (saponin buffer), and 10% goat serum for 30 min. 22E7 mAb or an IgG1 isotype control was added for 20 min, and the cells were washed twice in saponin buffer. The GaM/FITC secondary Ab was added for 20 min, and the cells were washed twice in saponin buffer. Normal mouse serum was added for 20 min, and the cells again were washed twice in saponin buffer. After washing twice with PBS, 0.5% BSA, and 0.01% sodium azide, T6/RD1 mAb was added for 10 min, and the cells were finally washed twice in PBS, 0.5% BSA, and 0.01% sodium azide.

For determination of surface or intracellular IgE binding, the untreated or permeabilized cells were incubated with human myeloma IgE for 90 min at room temperature followed by counterstaining with anti-human IgE/FITC or an isotype control.

For investigation of FcRI expression, a permeabilization protocol using digitonin as a detergent was necessary. All of the following steps were performed at 4°C. EC were washed twice with PBS, fixed with PBS and 0.5% formaldehyde for 20 min, and washed with PBS four times. After addition of digitonin at a final concentration of 10 µg/ml for 5 min, the cells were washed once with PBS, 0.5% BSA, 0.01% sodium azide, and 10% goat serum, and mAb 4G8 or an IgG2b isotype control was added for 30 min. Then, the cells were washed three times with PBS, 0.5% BSA, 0.01% sodium azide, and 0.05% Tween-20, followed by an incubation step with GaM/FITC Ab for 30 min. The latter washing step was repeated, and the cells were incubated with normal mouse serum for 20 min. After washing the cells twice in PBS, 0.5% BSA, 0.01% sodium azide, and 0.05% Tween-20 and then using this buffer without Tween-20, surface labeling with the anti-CD1a mAb T6/RD1 was performed for 30 min, followed by two final washing steps with PBS, 0.5% BSA, 0.01% sodium azide, and 0.05% Tween-20. Control experiments without fixation and detergent for determination of surface-expressed structures or background fluorescence were performed with both permeabilization protocols.

For quantitative evaluation, the CD1a-positive population was gated out manually, and the percentage of FcRI- or FcRI-positive or IgE-binding cells was determined using LYSIS II software (Becton Dickinson). Gating on CD1a-negative cells, i.e., keratinocytes, was used as a negative control. For statistical evaluation of significances, the Mann-Whitney U test was performed with SPSS for Windows. Results are given as the mean percentage of positive cells ± SEM.

Amplification of mRNA and analysis of transcripts

Total RNA was extracted from highly purified LC, RBL-48, U937, Jurkat E6.1, or ECV304 cell lines using Trizol (Life Technologies, Eggenstein, Germany) following the manufacturer’s instructions. RT reactions were performed as previously described (5) using 1µg of total RNA. Denaturation at 94°C for 40 s was followed by annealing of the primers at 55°C for 30 s and extension at 72°C for 30 s. A final extension phase of 5 min was added. Specific primer sequences for each gene were as follows: human glyceraldehyde-6-phosphate dehydrogenase (GAPDH): sense, 5'-CCA CCC ATG GCA AAT TCC ATG GCA-3'; antisense, 5'-TCT AGA CGG CAG GTC AGG TCC ACC-3', yielding a fragment of 598 bp; rat GAPDH: sense, 5'-TGC CAC TCA GAA GAC TGT GG-3'; antisense, 5'-TGT GAG GGA GAT GCT CAG TG-3' (fragment of 575 bp); human FcRI: sense, 5'-CTG TTC TTC GCT CCA GAT GGC GT-3'; antisense, 5'-TAC AGT AAT GTT GAG GGG CTC AG-3' (fragment size 536 bp); human FcRI: sense, 5'-CCA GCA GTG GTC TTG CTC TTA C-3'; antisense, 5'-GCA TGC AGG CAT ATG TGA TGC C-3' (fragment of 338 bp); and tryptase: sense, 5'-CTC CCT CAT CCA CCC CCA GT-3'; antisense, 5'-GGA TCC AGT CCA AGT AGT AG-3' (fragment of 616 bp). Amplification was performed on a Perkin-Elmer GeneAmp PCR System 9600 thermocycler (Applied Biosystems, Weiterstadt, Germany). The PCR cycle numbers for the amplification of the respective cDNAs were 30 for GAPDH and 37 for FcRI and FcRI. Specific PCR fragments were separated on 0.8% agarose gels and visualized using ethidium bromide staining. The PCR products were evaluated semiquantitatively by comparing the ratio of the specific products vs the GAPDH band by digital image analysis using the WinCam system (Cybertech, Berlin, Germany).

Biochemical analysis of FcRI

LC-enriched EC were prepared as described above. After lysis in the presence of protease inhibitors, the proteins (14 µg/lane) were fractionated by electrophoresis on 10% SDS-PAGE for FcRI and 18% for FcRI and electrotransferred to nitrocellulose membranes. Lysates from RBL-48 cells, normal human PBMC, ECV304, and LC-depleted EC were used as controls. After blocking, proteins were identified using the Abs RAB1 for FcRI and 4D8 for FcRI (both at a final dilution of 1/1000). The bands were visualized with a peroxidase-conjugated goat anti-mouse or goat anti-rabbit Ig Ab followed by an enhanced chemiluminescence Western blot detection system (ECL, Amersham, Arlington Heights, IL) according to the manufacturer’s protocol.

	Results

Top Abstract Introduction Materials and Methods Results Discussion References

 
Evidence for the maintenance of an intracellular pool of FcRI in freshly isolated LC lacking surface receptor expression

We and others have previously reported that FcRI surface expression on freshly isolated LC is highly variable (6, 9, 12). Indeed, the highest FcRI surface expression was found in inflammatory skin diseases, specifically in lesional skin of AD, whereas in 10% of the examined samples of normal skin (n = 60) LC failed to express any detectable receptor moieties (referred to as FcRI^neg LC) even when using several reagents reacting with distinct epitopes of FcRI (not shown). Since we could not exclude that LC express at least one of the receptor components, we questioned whether FcRI^neg LC may contain intracellular receptor moieties. Therefore, as shown in Figure 1, surface (light panels) and intracellular (left panels) anti-FcRI stainings were performed with FcRI^neg (upper panels) and FcRI^pos (middle panels) LC obtained from normal and atopic skin, respectively. While permeabilization with low (10 µg/ml) concentrations of digitonin failed to reveal any staining in FcRI^neg cells, permeabilization with high (5 mg/ml) concentrations of saponin disclosed a strong intracellular anti-FcRI reactivity (84 ± 5%; n = 11) regardless of the surface expression (17 ± 10%). Unspecific labeling has been ruled out by analyzing FcRI^neg EC cells, i.e., keratinocytes (Fig. 1, lower panels). This strong intracellular signal was not due to the unmasking of hidden epitopes by saponin, since similar results were obtained with several reagents (21) reacting with distinct epitopes of FcRI (data not shown). When using FcRI^pos LC obtained from biopsies of lesional skin of AD (n = 4) containing LC with high FcRI surface expression (93 ± 8%), no significant variation in the intracellular staining could be noted (83 ± 9%). Thus, LC constitutively express an intracellular pool of FcRI-moieties regardless of FcRI surface levels.

View larger version (26K): [in this window] [in a new window]   FIGURE 1. Surface and intracellular expression of FcRI in LC. Freshly isolated EC containing FcRIneg or FcRIpos LC (upper four histograms) were obtained from normal skin (NS) or lesional skin of atopic dermatitis (AD), respectively, as described in Materials and Methods, and then subjected to double labeling with anti-CD1a/PE and either surface staining (right panels) or intracellular staining (left panels) after permeabilization with saponin, using the anti-FcRI mAb 22E7. LC were gated on their CD1a expression, and the stainings were shown as overlays with the respective isotype control. Keratinocytes (lower two histograms) were used as negative controls.

Characterization of intracellular FcRI

In previous reports, amplification of total RNA from FcRI^neg LC using primers spanning the transmembrane domain of FcRI yielded a single PCR product (5, 6), excluding the possibility of a splicing variant lacking the transmembrane domain.

Since intracellular sequestration of FcRI could be due to variations in N-linked glycosylation of the N-terminal portion of FcRI, which seems to be critical to the folding machinery in the endoplasmic reticulum and subsequently to the surface expression (27), we addressed this possibility by performing immunoblot analyses of lysates from FcRI^neg LC and FcRI^pos LC. However, as shown in Figure 2A, under both conditions (lanes 3 and 4), a reactive band of the expected molecular mass of 45 to 66 kDa, but not in the range of 24 kDa, which would have been compatible with the unglycosylated protein backbone, was detectable. The band at 30 kDa was identified as galectin-3 by immunoblotting using a recombinant protein produced in our laboratory (data not shown). Lysates from RBL-48 cells transfected with the gene of the human FcRI revealed the same reactivity (lane 1).

View larger version (25K): [in this window] [in a new window]   FIGURE 2. Biochemical analysis of intracellular FcRI and IgE binding in FcRIneg and FcRIpos LC. A, FcRIneg LC (lane 4) and FcRIpos LC (lane 3) were isolated from normal skin as described in Materials and Methods. RBL-48 stably transfected with the human FcRI gene (lane 1), ECV304 cells (lane 2), and LC-depleted EC (lane 5) were used as positive and negative controls, respectively. Cells were lysed, and the proteins were separated by 10% SDS-PAGE, electroblotted onto nitrocellulose, and incubated with the anti-FcRI Ab RAB1. Molecular mass standards (in thousands) are shown on the left. B, Freshly isolated FcRIneg LC were obtained from normal skin as described in Materials and Methods, then IgE binding was tested without or with permeabilization with saponin.

Thus, from this series of experiments we conclude that LC express an intracellular form of FcRI that is able to bind IgE.

The presence of FcRI correlates with the surface expression of the intracellularly preformed FcRI on LC

It has been suggested that FcRI is ubiquitously expressed on various types of hemopoietic cells as part of multimeric surface receptors (28). Furthermore, mouse mast cells lacking FcRI do not express surface FcRI (29). Finally, it has been reported that in the human system, the presence of FcRI is necessary and sufficient for the surface expression of FcRI and related structures and the function of the receptor complexes (30, 31, 32). Therefore, we investigated the presence of FcRI in LC with different levels of surface receptor expression.

In the first approach, we performed semiquantitative analysis of PCR products for human FcRI (Fig. 3A). The presence of the transcripts correlated to the receptor surface expression (n = 5; r = 0.91; p < 0.03). To verify whether FcRI transcripts also lead to protein synthesis, LC were analyzed for their FcRI surface expression and were permeabilized by a low digitonin concentration, which is known to leave multimeric surface structures such as the TCR undamaged (26), for the detection of FcRI protein levels. Permeabilization with high concentrations of saponin did not lead to staining of FcRI regardless of FcRI surface levels, suggesting a solubilization of surface-expressed multimeric structures such as FcRI. While no or very low amounts of FcRI were detected in FcRI^neg LC, which have been demonstrated to contain a high level of intracellular FcRI protein (Figs. 1 and 2A) despite the absence of receptor surface expression, clear-cut reactivity was observed in LC expressing surface receptor, and most importantly, there was a significant correlation between the expression of surface FcRI and FcRI at the protein level (n = 8; r = 0.89; p < 0.005; Fig. 3, B andC). CD16, which could associate with FcRI, has never been detected on these cells (data not shown). In addition, another structure that could be associated with FcRI, the -chain of the TCR, was not found to be expressed in LC after performing RT-PCR, intracellular staining in flow cytometry, and immunoblotting (data not shown).

View larger version (19K): [in this window] [in a new window]   FIGURE 3. FcRI modulates the surface expression of FcRI in LC. A, PCR analysis of the transcripts for human FcRI, FcRI, tryptase, and GAPDH in LC with various surface expressions, RBL-48 cells (RBL cells transfected with human FcRI, which associates with rat FcRI), T cells, Jurkat cells, and U937 cells as controls. B, Correlation between the surface expression of FcRI and the presence of FcRI on LC determined by flow cytometry. The percentage of positive cells for FcRI was plotted for LC with various FcRI surface expressions. C, LC expressing high (upper histograms) and low (lower histograms) amounts of surface FcRI were tested for the presence of FcRI. EC were subjected to double labeling with anti-CD1a/PE and surface staining using the anti-FcRI mAb 22E7 (right panels) or to intracellular staining using the anti-FcRI mAb 4D8 after permeabilization (left panels). LC were gated on their CD1a expression, and the stainings were shown as overlays with the respective isotype control. D, Western blot of FcRI from FcRIpos and FcRIneg LC. FcRIneg LC (lane 4) and FcRIpos LC (lane 3) were isolated from normal skin and subjected to immunoblot as described in Figure 2. Normal human PBMC (lane 1) were used as a positive control. ECV304 (lane 2) and LC-depleted EC (lane 5) were used as negative controls.

Lack of detectable transcripts for FcRI, but not for FcRI, upon in vitro maturation of LC

It has been demonstrated that resident or freshly isolated LC are immature DC that, after Ag capture, undergo profound phenotypical and functional alterations during their migration to the regional lymph nodes (33). This maturation into potent stimulatory cells is reproduced in vitro by short term culture and supported by GM-CSF (34). Therefore, we asked whether this maturation is accompanied by changes in the expression of FcRI and its subunits.

Freshly isolated LC (n = 6) were cultured in the presence of GM-CSF for 36 h, and their FcRI expression was analyzed. We observed a dramatic decrease in the surface expression of FcRI on LC leading to nearly negative cells by 36 h (0 h, 27 ± 15%; 36 h, 2 ± 7%; p < 0.05). This down-regulation was also detected on spontaneously emigrating LC (data not shown) prepared without a trypsinization procedure. Similarly, the intracellular pool of FcRI and transcripts rapidly disappeared after a short culture, suggesting that differentiating LC dramatically down-regulate their FcRI protein synthesis (0 h, 85 ± 5%; 36 h, 3 ± 7%; p < 0.0001; Fig. 4A) and probably gene transcription (Fig. 4B). In contrast, FcRI (Fig. 4A) and its transcripts (Fig. 4B) were still found in cultured LC, indicating a possible additional role of a shedding process in the down-regulation of surface FcRI.

View larger version (38K): [in this window] [in a new window]   FIGURE 4. Loss of FcRI expression upon in vitro maturation of LC. A, Freshly isolated (left panels) and 24-h-cultured (right panels) LC were tested for expression of FcRI and FcRI by flow cytometry. They were subjected to double labeling with anti-CD1a/PE and intracellular staining after permeabilization, using the anti-FcRI mAb 22E7 and the anti-FcRI mAb 4D8. LC were gated on their CD1a expression, and the stainings were shown as overlays with the respective isotype control. B, PCR analysis of transcripts for FcRI and FcRI in highly purified freshly isolated (lane 3) and 24-h-cultured (lane 4) LC. RBL-48 (FcRI) or U937 (FcRI; lane 1), and ECV304 (lane 2) were used as positive and negative controls, respectively.

	Discussion

Top Abstract Introduction Materials and Methods Results Discussion References

 
We and others have previously reported on the great variation of FcRI surface expression on human APCs, including LC, monocytes, and inflammatory dendritic EC (5, 6, 7, 9). Since this phenomenon seems to be important for the receptor function (12), understanding the mechanisms underlying the regulation of the FcRI surface expression in vivo is of crucial importance. In the present study we provide the first insight into the mechanisms involved in the regulation of the surface expression of human FcRI in freshly isolated LC.

Analysis of PCR products and biochemical characterization of the preformed intracellular FcRI moieties indicate that the presence of transmembrane-deleted splice variants is unlikely and disclose a mature form of this FcRI subunit. Thus, based on these observations, we speculate that these preformed FcRI-chains are most likely stored in the endoplasmic reticulum. This is further supported by the fact that permeabilization of LC with 5 mg/ml saponin, which is known to permeabilize not only the plasma membrane but also intracellular organelles such as rough endoplasmic reticulum when used at high concentrations (40), showed strong reactivity for FcRI. In contrast, permeabilization with 10 µg/ml digitonin, which at low concentrations has been reported to selectively permeabilize the cholesterol-rich plasma membrane while leaving the membranes of intracellular organelles, which are poor in cholesterol (41), intact (42, 43, 44, 45), did not lead to staining of intracellular FcRI (for a summary of the properties of digitonin and saponin, see 46 . It is unlikely that this massive amount of -chains is due to cryptic receptors hidden in the plasma membrane approached only by specific procedures (e.g., the effect of saponin or cell lysis for subsequent immunoblotting), because in the investigated FcRI^neg LC, the FcRI -chains were absent or expressed in very low amounts. To our current knowledge, there are no reports of surface-expressed FcRI containing only an -chain but no ß- or -chains.

FcRIII has been reported to contain a sequence in its transmembrane domain that promotes its rapid degradation in the endoplasmic reticulum when not associated with FcRI (47). The transmembrane domain of FcRIII shows 62% sequence homology to that of FcRI and contains a sequence of eight conserved amino acids near the cytoplasmic domain of FcRI (48, 49) with an aspartic acid residue whose mutation reduced association of FcRIII with FcRI as well as its susceptibility to degradation (50). In the same report, similar regulatory mechanisms for FcRI have been proposed. However, to our knowledge, its intracellular degradation by such a mechanism has not been documented to date. Moreover, the exact localization of this sequence within the transmembrane domain of FcRIII has not been determined exactly. In TCR regulation (51) only a short sequence of nine amino acids within the transmembrane domain promotes rapid degradation of TCR- in the absence of CD3-. In the case of FcRIII, there is no evidence that such a sequence lies within the sequence conserved between FcRIII and FcRI. It also has been reported that Tac-1/IL2-R, which shows relative sequence homology to TCR- even within the short sequence responsible for degradation (five of nine amino acids), is not degraded but is transported to the cell surface (51). This indicates that relative sequence homology may not lead to same consequences in terms of degradation, e.g., since protein conformation, as an additional determinant of protein degradation, could be different. Other events that could prevent FcRI from degradation in LC may be envisaged, e.g., post-translational modifications such as glycosylation, which could confer some protective properties preventing intracellular proteolysis of FcRI. In addition, structures other than FcRI that have not yet been detected may associate with FcRI, thus inhibiting its degradation.

Based on the current knowledge, several not mutually exclusive possibilities may explain the lack of surface expression of FcRI. First, FcRI is associated with a yet to be defined structure(s), as mentioned above, that precludes its coupling to FcRI. Second, the coupling mechanisms leading to the active association of FcRI and FcRI are deficient or themselves are subject to distinct regulatory signals in LC. Third, and most likely in the case of normal resident epidermal LC, FcRI, the partner of FcRI, is lacking or present only in low concentrations, thereby precluding its surface expression under nonpathologic situations. This is suggested by our data showing that LC negative for surface FcRI exhibit high amounts of intracellular FcRI, as demonstrated by intracellular staining in flow cytometry and Western blotting, but no or very low amounts of FcRI at the protein as well as the mRNA levels. Since human LC express neither FcRI/CD64 nor FcRIII/CD16, a competition between FcRI and FcRIII for the -chain, as recently reported in mast cells (52), seems unlikely. Most importantly, our observations are in line with transfection experiments that have revealed that unlike in the rodent system, FcRI, but not FcRIß, is mandatory for the surface expression of the human IgE-binding FcRI (53, 54).

Besides the fact that the genes coding for FcRI and FcRI are regulated differently, our observations also strongly imply that in contrast to cells of the monocyte/macrophage lineage, FcRI is not constitutively expressed in resident epidermal LC. Instead, based on our previous findings of a receptor up-regulation in various inflammatory skin conditions (9, 12, 13), this subunit seems to be induced by distinct signals provided by an inflammatory microenvironment in the skin. However, it is important to note that, on the one hand, the highest FcRI surface expression, i.e., the highest FcRI expression, is characteristic of atopic dermatitis (14), and, on the other hand, this high receptor expression strongly correlates with the IgE serum level (9). The fact that various cytokines thought to be involved in the pathophysiology of inflammatory skin diseases such as IL-4, IFN-, or TNF- had no effect on FcRI surface levels implicates a complex model of FcRI regulation, perhaps, besides a complex combination of cytokines, involving intercellular contacts mediated through adhesion molecules. Clearly, more information on the regulation of the gene encoding for FcRI is needed for a better understanding of the regulation of FcRI expression in LC.

Finally, based on the observation that one of the main functions of FcRI on monocytes, LC, and DC may be to allow IgE-mediated Ag capture (8, 15, 16), our finding of the loss of surface and intracellular expression of FcRI on LC during their maturation into lymphoid DC strongly suggests that the receptor expression and function on LC are confined to their physiologic stage of resident DC. Interestingly, this loss is the result of 1) the disappearance of FcRI transcripts, as witnessed in our PCR experiments, possibly combined with 2) a rapid degradation/shedding of the surface moieties, since the down-regulation of FcRI expression is much less pronounced. The concept that these regulatory principles for FcRI observed are restricted to immature DC, e.g., freshly isolated LC, is further substantiated by the absence of surface expression of FcRI when culturing LC in the presence of IL-4, which has been reported to induce FcRI gene transcription in eosinophils (55), in in vitro generated CD1a⁺ DC (R. Magerstaedt, J.W., E. Geiger, S.K., D.H., and T.B., manuscript in preparation), and in bone marrow-derived mast cells (39). The IgE level, which is another factor known to up-regulate the expression of FcRI on monocytes, basophils, and mast cells (35, 36, 37, 38), also shows no effect on FcRI on LC during maturation. Binding of IgE to surface FcRI is thought to stabilize the receptor complexes, inhibiting receptor internalization and thereby leading to an accumulation of newly synthesized FcRI on the cell surface. From that point of view it is obvious that in cultured LC, incubation with IgE shows no effect, since FcRI synthesis is rapidly down-regulated. This supports the concept of a differential regulation of FcRI on LC.

Taken together, we provide evidence for the first time that LC use a unique and to date unreported mechanism involving a constitutive pool of preformed intracellular FcRI. The surface expression of FcRI from this pool may be regulated by the variable presence of FcRI. This mechanism would allow the cells to rapidly and finely tune their FcRI expression and confers upon them a high versatility in a tissue constantly exposed to rapid changes in allergenic and environmental challenges. Whether these mechanisms are restricted to APC or whether FcRI expression in effector cells of anaphylaxis, i.e., mast cells and basophils, is subjected to similar mechanisms is not yet known.

	Acknowledgments

 
We are grateful to Dr. A. Wollenberg for providing skin specimens from patients with atopic dermatitis. We thank Dr. J. Kochan (Department of Autoimmune Diseases, Hoffmann-La Roche, Nutley, NJ) and Dr. Torbjörn Bjerke (Aarhus, Denmark) for providing the anti-FcRI reagents.

	Footnotes

 
¹ This work was supported by grants from the Deutsche Forschungsgemeinschaft (SFB 217/D4), Institut National de la Santé et de la Recherche Médicale (CJF 9403), and the Deutscher Akademischer Austauschdienst (312/pro-gg).

² Address correspondence and reprint requests to Dr. Thomas Bieber, Department of Dermatology, Friedrich Wilhelms University, Sigmund-Freud-Str. 25, 53105 Bonn, Germany. E-mail address:

³ Abbreviations used in this paper: FcRI, high affinity receptor for immunoglobulin E; LC, Langerhans cells; DC, dendritic cells; EC, epidermal cells; AD, atopic dermatitis; PE, phycoerythrin; GaM, goat anti-mouse; FcRI, -chain of high affinity receptor for immunoglobulin E; GM-CSF, granulocyte macrophage colony-stimulating factor; FcRI, -chain of high affinity receptor for immunoglobulin E; GAPDH, glyceraldehyde-6-phosphate dehydrogenase.

Received for publication November 18, 1997. Accepted for publication March 23, 1998.

	References

Top Abstract Introduction Materials and Methods Results Discussion References

 

1. Keegan, A. D., W. E. Paul. 1992. Multichain immune recognition receptors: similarities in structure and signalling pathways. Immunol. Today 13:63.[Medline]
2. Metzger, H.. 1992. The receptor with high affinity for IgE. Immunol. Rev. 125:37.[Medline]
3. Ravetch, J. V., J. P. Kinet. 1991. Fc receptors. Annu. Rev. Immunol. 9:457.[Medline]
4. Gounni, A. S., B. Lamkhioued, E. Delaporte, A. Capron, J. P. Kinet, M. Capron. 1994. High-affinity IgE receptor on eosinophils is involved in defence against parasites. Nature 367:183.[Medline]
5. Bieber, T., H. de la Salle, A. Wollenberg, R. Chizzonite, J. Hakimi, J. Ring, D. Hanau, C. de la Salle. 1992. Human Langerhans cells express the high affinity receptor for IgE (FcRI). J. Exp. Med. 175:1285.[Abstract/Free Full Text]
6. Wang, B., A. Rieger, O. Kilgus, K. Ochiai, D. Maurer, D. Födinger, J. P. Kinet, G. Stingl. 1992. Epidermal Langerhans cells from normal human skin bind monomeric IgE via FcRI. J. Exp. Med. 175:1353.[Abstract/Free Full Text]
7. Maurer, D., E. Fiebiger, B. Reininger, B. Wolffwiniski, M. H. Jouvin, O. Kilgus, J. P. Kinet, G. Stingl. 1994. Expression of functional high affinity immunoglobulin E receptors (FcRI) on monocytes of atopic individuals. J. Exp. Med. 179:745.[Abstract/Free Full Text]
8. Maurer, D., E. Fiebiger, C. Ebner, B. Reininger, G. Fischer, S. Wichlas, M. H. Jouvin, M. Schmitt-Egenolf, D. Kraft, J. P. Kinet, G. Stingl. 1996. Peripheral blood dendritic cells express FcRI as a complex composed of FcRI- and FcRI-chains and can use this receptor for IgE-mediated allergen presentation. J. Immunol. 157:607.[Abstract]
9. Wollenberg, A., S. Kraft, D. Hanau, T. Bieber. 1996. Immunomorphological and ultrastructural characterization of Langerhans cells and a novel, inflammatory dendritic epidermal cell (IDEC) population in lesional skin of atopic eczema. J. Invest. Dermatol. 106:446.[Medline]
10. Steinman, R. M.. 1991. The dendritic cell system and its role in immunogenicity. Annu. Rev. Immunol. 9:271.[Medline]
11. Bieber, T., J. Ring. 1992. In vivo modulation of the high affinity receptor for IgE, FcRI, on human epidermal Langerhans cells. Int. Arch. Allergy Clin. Immunol. 99:204.
12. Jurgens, M., A. Wollenberg, D. Hanau, H. de la Salle, T. Bieber. 1995. Activation of human epidermal Langerhans cells by engagement of the high affinity receptor for IgE, Fc epsilon RI. J. Immunol. 155:5184.[Abstract]
13. Bieber, T., M. Jürgens, A. Wollenberg, E. Sander, D. Hanau, H. de la Salle. 1995. Characterization of the protein tyrosine phosphatase CD45 on human epidermal Langerhans cells. Eur. J. Immunol. 25:317.[Medline]
14. Wollenberg, A., S. P. Wen, T. Bieber. 1995. Langerhans cells phenotyping: a new tool for the differential diagnosis of eczematous skin diseases. Lancet 346:1626.
15. Mudde, G., C. Bruijnzeel-Koomen, F. van Reijsen, G. Boland, P. Bruijnzeel-Koomen. 1989. IgE dependent allergen-presentation by epidermal Langerhans cells from patients with atopic dermatitis. Immunology 8:773.
16. Maurer, D., C. Ebner, B. Reininger, E. Fiebiger, D. Kraft, J. P. Kinet, G. Stingl. 1995. The high affinity immunoglobulin E receptor (FcRI) mediates IgE-dependent allergen presentation. J. Immunol. 154:6285.[Abstract]
17. Bieber, T.. 1996. FcRI on antigen-presenting cells. Curr. Opin. Immunol. 18:773.
18. Leung, D. Y. M.. 1995. Atopic dermatitis: the skin as a window into the pathogenesis of chronic allergic diseases. J. Allergy Clin. Immunol. 96:302.[Medline]
19. Bieber, T.. 1995. Role of Langerhans cells in the physiopathology of atopic dermatitis. Pathol. Biol. 43:871.[Medline]
20. Fithian, E., P. Kung, G. Goldstein, M. Rubenfeld, C. Fenoglio, R. Edelson. 1981. Reactivity of Langerhans cells with hybridoma antibody. Proc. Natl. Acad. Sci. USA 78:2541.[Abstract/Free Full Text]
21. Riske, F., J. Hakimi, M. Mallamaci, M. Griffin, B. Pilson, N. Tobkes, P. Lin, W. Danho, J. Kochan, R. Chizzonite. 1991. High affinity human IgE receptor (FcRI): analysis of functional domains of the -subunit with monoclonal antibodies. J. Biol. Chem. 266:11245.[Abstract/Free Full Text]
22. Schoneich, J. T., V. L. Wilkinson, H. Kado-Fong, D. H. Presky, J. P. Kochan. 1992. Association of the human FcRI subunit with novel cell surface polypeptides. J. Immunol. 148:2181.[Abstract]
23. Gilfillan, A. M., H. Kado-Fong, G. A. Wiggan, J. Hakimi, U. Kent, J. P. Kochan. 1992. Conservation of signal transduction mechanisms via the human FcRI after transfection into rat mast cell line, RBL-2H3. J. Immunol. 149:2445.[Abstract]
24. Bieber, T., A. Rieger, C. Neuchrist, J. C. Prinz, E. P. Rieber, G. Boltz-Nitulescu, O. Scheiner, D. Kraft, J. Ring, G. Stingl. 1989. Induction of FcR2/CD23 on human epidermal Langerhans cells by human recombinant interleukin 4 and -interferon. J. Exp. Med. 170:309.[Abstract/Free Full Text]
25. Ludewig, B., J. Holzmeister, M. Gentile, H. R. Gelderblom, K. Rokos, Y. Becker, G. Pauli. 1995. Replication pattern of human immunodeficiency virus type 1 in mature Langerhans cells. J. Gen. Virol. 76:1317.[Abstract/Free Full Text]
26. Vivier, E., P. Morin, Q. Tian, J. Daley, M. L. Blue, S. F. Schlossman, P. Anderson. 1991. Expression and tyrosine phosphorylation of the T cell receptor -subunit in human thymocytes. J. Immunol. 146:1142.[Abstract]
27. Letourneur, O., S. Sechi, J. Willettebrown, M. W. Robertson, J. P. Kinet. 1995. Glycosylation of human truncated FcRI chain is necessary for efficient folding in the endoplasmic reticulum. J. Biol. Chem. 270:8249.[Abstract/Free Full Text]
28. Moingeon, P., J. L. Lucich, E. L. Reinherz. 1992. Characterization of Fc epsilon RI gamma in human natural killer cells. Int. Immunol. 4:955.[Abstract/Free Full Text]
29. Ryan, J. J., C. A. Kinzer, W. E. Paul. 1995. Mast cells lacking the high affinity immunoglobulin E receptor are deficient in FcRI messenger RNA. J. Exp. Med. 182:567.[Abstract/Free Full Text]
30. Alber, G., L. Miller, C. L. Jelsema, N. Varin-Blank, H. Metzger. 1991. Structure-function relationships in the mast cell high affinity receptor for IgE: role of the cytoplasmic domains and of the beta subunit. J. Biol. Chem. 266:22613.[Abstract/Free Full Text]
31. Mao, S. Y., N. Varin-Blank, M. Edidin, H. Metzger. 1991. Immobilization and internalization of mutated IgE receptors in transfected cells. J. Immunol. 146:958.[Abstract]
32. van Vugt, M. J., I. A. F. M. Heijnen, P. J. A. Capel, S. Y. Park, C. S. Ra, T. Saito, J. S. Verbeek, J. G. J. van deWinkel. 1996. FcR-chain is essential for both surface expression and function of human FcRI (CD64) in vivo. Blood 87:3593.[Abstract/Free Full Text]
33. Schuler, G., R. M. Steinman. 1985. Murine epidermal Langerhans cells mature into potent immunostimulatory dendritic cells in vitro. J. Exp. Med. 161:526.[Abstract/Free Full Text]
34. Heufler, C., F. Koch, G. Schuler. 1988. Granulocyte/macrophage colony-stimulating factor and interleukin 1 mediate the maturation of murine epidermal Langerhans cells into potent immunostimulatory dendritic cells. J. Exp. Med. 167:700.[Abstract/Free Full Text]
35. Reischl, I. G., N. Corvaia, F. Effenberger, B. Wolffwiniski, E. Kromer, G. C. Mudde. 1996. Function and regulation of Fc epsilon RI expression on monocytes from non-atopic donors. Clin. Exp. Allergy 26:630.[Medline]
36. Yamaguchi, M., C. S. Lantz, H. C. Oettgen, I. M. Katona, T. Fleming, I. Miyajima, J. P. Kinet, S. J. Galli. 1997. IgE enhances mouse mast cell Fc epsilon RI expression in vitro and in vivo: evidence for a novel amplification mechanism in IgE-dependent reactions. J. Exp. Med. 185:663.[Abstract/Free Full Text]
37. MacGlashan, D. W., B. S. Bochner, D. C. Adelman, P. M. Jardieu, A. Togias, L. M. Lichtenstein. 1997. Serum IgE level drives basophil and mast cell IgE receptor display. Int. Arch. Allergy Immunol. 113:45.[Medline]
38. MacGlashan, D. W., B. S. Bochner, D. C. Adelman, P. M. Jardieu, A. Togias, J. McKenzie-White, S. A. Sterbinsky, R. G. Hamilton, L. M. Lichtenstein. 1997. Down-regulation of FcRI expression on human basophils during in vivo treatment of atopic patients with anti-IgE antibody. J. Immunol. 158:1438.[Abstract]
39. Toru, H., C. Ra, S. Nonoyama, K. Suzuki, J. Yata, T. Nakahata. 1996. Induction of the high-affinity IgE receptor (FcRI) on human mast cells by IL-4. Int. Immunol. 8:1367.[Abstract/Free Full Text]
40. Strous, G. J., P. van Kerkhof. 1989. Release of soluble resident as well as secretory proteins from HepG2 cells by partial permeabilization of rough-endoplasmic-reticulum membranes. Biochem. J. 257:159.[Medline]
41. Colbeau, A., J. Nachbaur, P. M. Vignais. 1971. Enzymatic characterization and lipid composition of rat liver subcellular membranes. Biochim. Biophys. Acta 249:462.[Medline]
42. Fiskum, G., S. W. Craig, G. L. Decker, A. L. Lehninger. 1980. The cytoskeleton of digitonin-treated rat hepatocytes. Proc. Natl. Acad. Sci. USA 77:3430.[Abstract/Free Full Text]
43. Mackall, J., M. Meredith, M. D. Lane. 1979. A mild procedure for the rapid release of cytoplasmic enzymes from cultured animal cells. Anal. Biochem. 95:270.[Medline]
44. Plutner, H., H. W. Davidson, J. Saraste, W. E. Balch. 1992. Morphological analysis of protein transport from the ER to Golgi membranes in digitonin-permeabilized cells: role of the p58 containing compartment. J. Cell Biol. 119:1097.[Abstract/Free Full Text]
45. Schmalzing, G., S. Kröner, H. Passow. 1989. Evidence for intracellular sodium pumps in permeabilized Xenopus laevis oocytes. Biochem. J. 260:395.[Medline]
46. Schulz, I.. 1990. Permeabilizing cells: some methods and applications for the study of intracellular processes. Methods Enzymol. 192:280.[Medline]
47. Kurosaki, T., I. Gander, J. V. Ravetch. 1991. A subunit common to an IgG Fc receptor and the T-cell receptor mediates assembly through different interactions. Proc. Natl. Acad. Sci. USA 88:3837.[Abstract/Free Full Text]
48. Kochan, J., L. F. Pettine, J. Hakimi, K. Kishi, J. P. Kinet. 1988. Isolation of the gene coding for the subunit of the human high affinity IgE receptor. Nucleic Acids Res. 16:3584.[Free Full Text]
49. Scallon, B. J., E. Scigliano, V. H. Freedman, M. C. Miedel, Y.-C. E. Pan, J. C. Unkeless, J. P. Kochan. 1989. A human immunoglobulin G receptor exists in both polypeptide-anchored and phosphatidylinositol-glycan-anchored forms. Proc. Natl. Acad. Sci. USA 86:5079.[Abstract/Free Full Text]
50. Kurosaki, T., J. V. Ravetch. 1989. A single amino acid in the glycosyl phosphatidylinositol attachment domain determines the membrane topology of FcRIII. Nature 342:805.[Medline]
51. Bonifacino, J. S., P. Cosson, R. D. Klausner. 1990. Colocalized transmembrane determinants for ER degradation and subunit assembly explain the intracellular fate of TCR chains. Cell 63:503.[Medline]
52. Dombrowicz, D., V. Flamand, I. Miyajima, J. V. Ravetch, S. J. Galli, J. P. Kinet. 1997. Absence of Fc (epsilon) RI alpha chain results in upregulation of FcRIII-dependent mast cell degranulation and anaphylaxis: evidence of competition between FcRI and FcRIII for limiting amounts of FcR beta and gamma chains. J. Clin. Invest. 99:915.[Medline]
53. Miller, L., U. Blank, H. Metzger, J. P. Kinet. 1989. Expression of high affinity binding of human immunoglobulin E by transfected cells. Science 244:334.[Abstract/Free Full Text]
54. Alber, G., L. Miller, C. L. Jelsema, N. Varin-Blank, H. Metzger. 1991. Structure-function relationships in the mast cell high affinity receptor for IgE: role of the cytoplasmic domains and of the ß subunit. J. Biol. Chem. 266:22613.
55. Terada, N., A. Konno, Y. Terada, S. Fukuda, T. Yamashita, T. Abe, H. Shimada, K. Ishida, K. Yoshimura, Y. Tanaka, C. Ra, K. Ishikawa, K. Togawa. 1995. IL-4 upregulates Fc epsilon RI -chain messenger RNA in eosinophils. J. Allergy Clin. Immunol. 96:1161.[Medline]

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