|
|
||||||||

* Department of Dermatology and
Department of Neurology and Neuroscience, Weill Cornell Medical College, New York, NY 10021
| Abstract |
|---|
|
|
|---|
production. CGRP also inhibited stimulated production of the Th1 chemokines CXCL9 and CXCL10 but induced production of the Th2 chemokines CCL17 and CCL22 by a dendritic cell line and by freshly obtained LC. Changes in production of these chemokines correlated with the effect of CGRP on mRNA levels for these factors. Exposure of LC to nerve-derived CGRP in situ may polarize them toward favoring Th2-type immunity. | Introduction |
|---|
|
|
|---|
In this regard, the finding that LC can produce both Th1- and Th2-type chemokines suggests they participate in determining the character of immunity that is engendered in the skin or in draining lymph nodes after trafficking of LC to those sites. As LC in situ in the skin are frequently anatomically associated with calcitonin gene-related peptide (CGRP)-containing nerves (5), the possibility that CGRP influences the ability of LC to support Th1- or Th2-type immunity must be considered. Based on our earlier work showing that CGRP inhibits LC Ag presentation in several models including presentation to a Th1 clone (5, 6, 7), we hypothesized that CGRP may act by biasing LC toward inducing Th2-type immunity.
Chemokines are chemotactic cytokine signals involved in leukocyte migration. CD4+ Th1 and Th17 cells express CXCR3 while Th2 cells predominantly express CCR4 (8, 9). It has been recently found that IFN-
, LPS, and polyinosinic-polycytidylic acid induce production of the Th1-type chemokines CXCL9 (monokine induced by IFN-
) and CXCL10 (IP-10) by murine LC (10). These chemokines bind to CXCR3 and promote the migration of Th1 cells. The Th2-type chemokines CCL17 (thymus and activation-regulated chemokine) and CCL22 (macrophage-derived chemokine) promote the migration of Th2 cells via binding to CCR4. CXCR3 is also expressed by NK cells, and Th1-type cytokines are involved in their migration (11). CXCR3 signaling plays a role in experimental autoimmune encephalitis and murine models of herpes simplex encephalitis, corneal and skin disease, and multiple sclerosis, among others (12, 13). CCR4 signaling is also involved in various other disorders including asthma and, interestingly, CCR4 signaling is believed to play a significant role in some types of malignancies (14, 15). For example, in a subset of patients with CCR4+ T cell leukemia or lymphoma, the tumor cells themselves function as regulatory T cells, contributing to tumor survival in the face of host anti-tumor immunity (15). In other examples, CCL17 and CCL22 are sometimes produced by tumor cells and attract CCR4+ T regulatory cells to the tumor where they create an environment permissive for tumor escape from host immune responses (15). Overall, CCR3 and CCR4 signaling play crucial roles in determining the balance of Th1 vs Th2 immunity in many situations.
The experiments discussed in this paper evaluated the possibility that exposure of LC to CGRP may differentially modulate the ability of these cells to present Ag to Th1 and Th2 cells. The ability of CGRP to regulate the production of Th1 and Th2 chemokines, and thereby regulate the nature of a cutaneous immune response, was also evaluated. Some experiments were initially performed with XS106 cells [a dendritic cell line derived from neonatal BALB/c epidermis (16, 17)] as a surrogate for LC. All experiments other than Northern blotting were also performed with fresh, primary LC. The results discussed below strongly suggest that CGRP biases LC toward favoring Th2-type immune responses.
| Materials and Methods |
|---|
|
|
|---|
Six- to 12-wk-old female BALB/c (H-2d), A/J (H-2k), and DO11.10 chicken OVA (cOVA) TCR Tg mice on a BALB/c background [C.Cg-Tg(DO11.10)10Dlo/J] mice were purchased from The Jackson Laboratory and were kept in the animal facility of Weill Medical College of Cornell University on a 12-h light/dark cycle. All experiments were approved by the Institutional Animal Care and Use Committee of the Weill Cornell Medical College.
Reagents
-CGRP and
-CGRP8–37 were purchased from Bachem. Conalbumin and keyhole limpet hemocyanin (KLH) were purchased from Sigma-Aldrich. A fragment of cOVA (cOVA323–339) was obtained from Peptides International.
Media and cell lines
Complete medium (CM) consisted of RPMI 1640 (Mediatech), 10% FCS (Gemini Biotech), 100 U/ml penicillin, 100 µg/ml streptomycin, 0.1 mM nonessential amino acids, 0.1 mM essential amino acids, 2 mM L-glutamine, 1 mM sodium pyruvate, and 10 mM HEPES buffer (all from Mediatech).
The XS106 cell line is a dendritic cell line derived from neonatal A/J epidermis. It is capable of Ag presentation and has many of the phenotypic characteristics of LC (16, 17). XS106 cells were grown in CM with the addition of 2 ng/ml murine rGM-CSF (Chemicon International), 10% NS cell supernatant [supernatant conditioned by a fibroblast-like cell line, known to support the growth of epidermal APC-derived cell lines (18)] and 5 x 10–5 M 2-ME (Sigma-Aldrich).
The HDK-1 cell line, a KLH-specific, I-Ad-restricted Th1 clone (19), was maintained in CM supplemented with 5 x 10–5 M 2-ME, 10 ng/ml murine IL-2 (Chemicon International), and 10% FCS (Gemini Biotech). The D10.G4.1 cell line (ATCC) is a conalbumin-specific, I-Ak-restricted Th2 clone (20). It was maintained in modified RPMI 1640 (American Type Culture Collection), supplemented with 0.05 mM 2-ME, 10 pg/ml mouse IL-1
(R&D Systems), 10% FCS (American Type Culture Collection), and 10% T-STIM with Con A (rat IL-2 culture supplement; BD Biosciences).
Preparation of epidermal cells (EC), LC-enriched EC (eEC), and purified LC (pLC)
EC were prepared using a modification of standard protocol (21). Briefly, the truncal skins of mice were shaved and chemically depilated. The s.c. fat and carnosus panniculus were removed by blunt dissection. The skins were then floated dermis side down for 45 min in Ca2+/Mg2+-free PBS containing 0.5 U of dispase/ml (BD Biosciences) and 0.38% trypsin (BD Biosciences). Epidermal sheets were collected by gentle scraping, washed, and dissociated by continuous mild agitation for 20 min in HBSS (Mediatech) supplemented with 2% FCS. The EC were then filtered through a 40-µm cell strainer (BD Biosciences) to yield EC containing
2–3% LC.
To prepare eEC, EC were incubated in a 1/2000 dilution of anti-Thy-1.2 mAbs (Sigma-Aldrich) for 30 min at 4°C. Low-toxicity rabbit complement (Cederlane Laboratories) was added at a 1/40 dilution for another 30 min at 37°C. Dead cells were digested by treatment with 0.05% trypsin and 80 µg/ml DNase I (Sigma-Aldrich) for 4 min at room temperature. Finally, the cells were washed in CM. This procedure enriches LC content by selectively removing epidermal T cells and some keratinocytes. FACS analysis has shown that the resulting population consists of
12% LC.
To prepare pLC, eEC were incubated with anti I-Ad mAbs (BD Biosciences) at a 1/50 dilution for 30 min at 4°C. They were then incubated with goat anti-mouse IgG conjugated to magnetic microspheres (Dynabeads M-450; Dynal Biotech) for 10 min with continuous, gentle agitation. The cells were then washed repeatedly (up to five times) to enrich LC, using a magnetic particle concentrator (Dynal Biotech) which adhered to the beads. By FACS analysis (using anti-I-Ad mAbs), this procedure yields a cell population of
95% LC.
CGRP receptor mRNA detection by RT-PCR
EC from BALB/c mice were obtained as described above and incubated with PE-conjugated anti-mouse I-Ad (BD Biosciences). Then LC were sorted by FACS on a FACScan (BD Biosciences). Total RNA was extracted from these freshly obtained LC as well as from XS106 cells using a total RNA extraction kit (Qiagen). RNase free DNase (Qiagen) was used to eliminate any contamination with genomic DNA. Then, 200 (LC) or 100 ng (XS106 cells) of RNA was reverse-transcribed into complementary DNA using 200 U of Superscript II reverse-transcriptase (Invitrogen) following the instructions of the manufacturer (Invitrogen). One-tenth of the synthesized cDNA was amplified by PCR using gene-specific primers made from published sequences for RAMP1, RAMP2, and RAMP3 (22). Primer sequences for calcitonin receptor-like receptor (CRLR) and CGRP-receptor component protein (CRCP) were designed from GenBank sequences for the mRNA of mouse CRLR and CRCP: CRLR, 5'-CTACTATTTTCTGCTTCTTT-3' forward and 5'-TTTGTGCTTATTTTCTTTCC-3' reversed; CRCP, 5'-TGGCGGAATAGGAGATAAGA-3' forward and 5'-AGACAGAAGGGACCGCATAA-3' reversed. The PCR products were electrophoresed in 1.5% agarose gel, stained with ethidium bromide, and visualized with UV radiation.
In vitro Ag presentation to Th1 and Th2 clones
To examine the effect of CGRP on LC Ag presentation to Th1 and Th2 clones in vitro, EC or pLC were prepared from A/J or BALB/c mice and plated in 96-well round-bottom plates at 1 x 105 cells/well (EC) or 1 x 104 cells/well (pLC) in CM. They were then incubated with varying concentration of CGRP (0.1, 1, 10, and 100 nM) at 37°C. After 2.5 h, cells from A/J were exposed to conalbumin and cells from BALB/c were exposed to KLH at a final concentration of 100 µg/ml, still in the presence of CGRP. After an additional 2.5 h, cells were extensively washed with CM. Then, A/J cells were cocultured with D10.G4.1 cells (Th2) (104 cells/well) and cells from BALB/c mice were cocultured with HDK cells (Th1) (104 cells/well). Supernatants were collected after 24 (Th2) or 72 h (Th1), respectively. IL-4 production by D10.G4.1 cells was measured by a sandwich ELISA kit (R&D Systems). IFN-
production by HDK cells was analyzed by a sandwich ELISA using purified rat anti-mouse IFN-
monoclonal capture Abs, biotinylated rat anti-mouse IFN-
monoclonal detection Abs, avidin-HRP (1/1000 dilution), and ABTS substrate, read at 405 nm (all reagents BD Biosciences).
Ag presentation to DO11.10 Tg T cells
Spleens were isolated from DO11.10 Tg mice and mechanically disrupted to yield a single cell suspension. Erythrocytes were then lysed by brief exposure to hypotonic medium. Then, splenocytes were passed through a nylon-wool column to yield a suspension of cells enriched for T cell content ("T cells"). pLC from BALB/c mice were cultured for 3 h in CM containing 10 nM CGRP or medium alone. Then, cells were washed three times and cocultured in 96-well round-bottom plates with DO11.10 T cells. Ten thousand CGRP treated or untreated pLC were cultured in each well with 1 x 105 T cells (for IFN-
assay) or 2 x 105 T cells (for IL-4 assay) in 200 µl of CM along with varying concentrations of cOVA323–339 in triplicate. Supernatants were harvested 48 h later, and content of IL-4 and IFN-
was assessed by sandwich ELISA kits (R&D Systems).
Preparation of culture supernatants
XS106 cells and pLC were cultured at a concentration of 0.5 x 106 cells per well in 6-well plates, stimulated with or without 100 ng/ml IFN-
in the presence or absence of varying concentration of CGRP. Supernatants were collected at different times and CXCL9, CXCL10, CCL17, and CCL22 content was measured by sandwich ELISA kits (R&D Systems) according to the manufacturers protocol.
RNA extraction and Northern blot analysis
XS106 cells were cultured at a concentration of 5 x 106 cells per 100 mm tissue culture dish and cultured with or without 100 ng/ml IFN-
in the presence or absence of CGRP (10 nM) for 12 h. Cells were collected and total cellular RNA extracted by TRIzol (Invitrogen), according to the manufacturers protocol. Then, 10 µg of total RNA was electrophoresed on 1.5% agarose-formaldehyde gels, transferred in 20x SSC onto a Hybond-N+ membrane (Amersham Biosciences), and cross-linked to the membrane using UV light.
Probes for murine chemokines and GAPDH were generated by RT-PCR using specific primers for CXCL9 (23), CXCL10 (24), CCL17 (25), and CCL22 (26). Oligonucleotides were end-labeled with 32P-dCTP (PerkinElmer) by using Klenow fragment of DNA polymerase I (Invitrogen). The RNA-containing membranes were prehybridized for 24 h at 42°C and hybridized for 24 h at 45°C with labeled probes [106 cpm] in Hybrisol-1 buffer (Millipore). The membranes were then washed twice in 2x SSC containing 0.1% SDS (20 min; 25°C) and once with 0.1% SSC containing 0.1% SDS (10 min; 55°C). The membranes were then exposed to x-ray film (Kodak). The intensity of the transcript was digitized and quantified using a phosphor imaging system (Typhoon Trio+; GE Healthcare) and then normalized to the intensity of GAPDH mRNA with results expressed as fold-increase over the level obtained with medium alone.
Statistics. The significance of differences between groups was assessed by Students two-tailed t test for unpaired values.
| Results |
|---|
|
|
|---|
The ability of eEC and
95% pLC to present conalbumin to the responsive Th2 clone D10.G4.1 (27) was examined. These cells respond to presentation of conalbumin by I-Ak. As shown in Fig. 1a, CGRP treatment of eEC (upper panel) and pLC (lower panel) dose-dependently increased their ability to present conalbumin to the Th2 clone D10.G4.1. In contrast, as shown in Fig. 1b, CGRP dose-dependently induced a decrease in the response of the Th1 clone HDK-1 (28) to presentation of KLH by eEC (upper panel) and pLC (lower panel). As a control, additional experiments were performed examining the ability of substance P (a neuropeptide that colocalizes with CGRP in sensory nerves) to modulate the ability of ECs enriched for LCs content to present Ag to the D10.G4.1 clone. Substance P had no affect on presentation to the clone (data not shown).
|
CGRP treatment of pLC enhances the IL-4 response while diminishing the IFN-
response of T cells from DO11.10 cOVA Tg mice upon presentation of cOVA
DO11.10 Tg mice carry a MHC class II-restricted rearranged TCR transgene and react to cOVA323–339 (29, 30). The transgene contains rearranged TCR
-chain and TCR β-chain genes and is expressed in the majority of T cells. These rearranged genes encode a cOVA-specific MHC class II (I-Ad)-restricted TCR. We used T cells from these mice as a second measure of the ability of CGRP to bias LC toward presenting Ag for a Th2 response. BALB/c pLC were cultured in CGRP or medium alone, washed, and then cocultured with DO11.10 T cells in the presence of varying concentrations of cOVA323–339. After 48 h, conditioned supernatants were harvested and assayed for IL-4 and IFN-
content by ELISA. As shown by the data in Fig. 2a, exposure to CGRP significantly enhanced the IL-4 response of DO11.10 Tg T cells. In contrast, as shown in Fig. 2b, exposure of pLC to CGRP diminished the IFN-
response.
|
Both the dendritic cell line XS106, derived from neonatal A/J epidermis, and fresh primary LC isolated by FACS from BALB/c EC were examined for expression of mRNA for the CGRP receptor by RT-PCR. As shown by the data in Fig. 3, both XS106 cells and primary fresh LC were found to express all of the components of the CGRP receptor.
|
We next examined the ability of CGRP to modulate the production of Th1 chemokines. XS106 cells were stimulated with 100 ng/ml IFN-
in the presence or absence of various concentrations of CGRP. After 72 h of culture, supernatants were harvested and CXCL9 and CXCL10 content assayed by ELISA. As shown by the data in Fig. 4a, exposure to IFN-
led to significant production of these chemokines and production of each chemokine was reduced in a dose-dependent fashion by the presence of CGRP. This finding was confirmed at the mRNA level by Northern blotting (Fig. 4b). CGRP also inhibited the production of both CXCL9 and CXCL10 by pLC stimulated with IFN-
in a similar manner (Fig. 4c). The ability of CGRP to inhibit the stimulated release of CXCL9 and CXCL10 from XS106 cells could be blocked by the presence of the type 1 CGRP receptor antagonist CGRP8–37 (data not shown).
|
We also evaluated the ability of CGRP to induce release of the Th2 chemokines CCL17 and CCL22. XS106 cells were cultured in medium containing 0–100 nM CGRP or medium alone. Supernatants were collected after 72 h of culture and assayed for CCL17 and CCL22 content by ELISA. As shown by the data in Fig. 5a, CGRP dose-dependently increased production of CCL17 and CCL22 by XS106 cells. This effect could also be observed at the mRNA level by Northern blotting (Fig. 5b). CGRP treatment of pLC in the same manner also increased CCL17 and CCL22 production (Fig. 5c). Interestingly, this effect of CGRP could not be inhibited by CGRP8–37 (data not shown). Thus, it is likely that this latter effect is not mediated by the CGRP1 receptor. CGRP is known to also activate the calcitonin like-receptor when associated with RAMP3 in transfected cell models (31) and it is likely acting on XS106 cells and LC in the same manner.
|
| Discussion |
|---|
|
|
|---|
We have hypothesized that the observation that LC are frequently anatomically associated with epidermal nerves containing CGRP may be relevant to the possibility that in the steady-state LC subserve a primarily down-regulatory or immunosuppressive role, perhaps to prevent unwanted immune reactivity against self-Ags or commensal microorganisms. We and others (5, 7) have previously shown that CGRP treatment of LC in vitro inhibits their ability to present Ag in several assays in vitro. Additionally, treatment of CGRP ex vivo inhibits their ability to used to immunize naive mice upon s.c. injection and immunization of mice with a contact sensitizer applied to a site injected intradermally with CGRP leads to a suppressed degree of sensitivity (6). We have now extended these observations to demonstrate that CGRP biases LC toward favoring functioning for Th2-type immunity.
We found that CGRP treatment of LC augmented their ability to present Ag to a Th2 clone while inhibiting Ag presentation to a Th1 clone. Similarly, treatment of LC with CGRP led to a decreased ability to present cOVA323–339 to DO11.10 Tg T cells for a Th1 response (IFN-
production) while augmenting a Th2 response (IL-4 production). CGRP also induced production of the Th2 chemokines CCL17 and CCL22 by XS106 cells and pLC. In the case of the Th1 chemokines CXCL9 and CXCL10, CGRP treatment resulted in inhibition of the stimulated production of these chemokines. With XS106 cells, we examined mRNA levels of these chemokines and the mRNA levels correlated with the effects of CGRP on expression of each of the chemokines at the protein level. To examine the possibility that any of these effects could be due to changes in viability of LC or T cells induced by exposure of LC to CGRP, we examined the viability of pLC in culture over time in 0, 0.1, 1, 10, and 100 nM CGRP. No significant differences in viability were observed (data not shown). To examine possible differences in viability of HDK-1 cells when Ag presentation is performed with LC treated with CGRP, we set-up experiments where LC were used with and without pretreatment with CGRP before being used to present KLH to HDK-1 cells. At the end of 72 h, HDK-1 cells were enumerated by performing FACS analysis for CD3. No significant difference in the number of HDK-1 cells was observed between the two conditions (data not shown).
It is likely that exposure of LC to CGRP from associated nerves in situ in the epidermis maintains LC in a state that favors activation of Th2 mechanisms over Th1 mechanisms and this effect may account, at least in part, for the immunosuppressive activities of LC with regard to Th1-type immunity. It has long been known that culture of EC in vitro leads to enhanced LC Ag presenting capability for some assays of APC function (39). Although exposure to GM-CSF and other stimulatory cytokines in culture (from contaminating keratinocytes) may account for some of this maturation, removal from an environment containing CGRP may also play a role. As a whole, these results support the concept of a locus of interaction between the nervous system and the immune system within the skin by which the nervous system is able to regulate the character of the cutaneous immune response. Furthermore, these findings might suggest practical new avenues for manipulation of cutaneous immunity through activation or inhibition of CGRP receptors.
| Disclosures |
|---|
|
|
|---|
| Footnotes |
|---|
1 This work was supported by National Institutes of Health Grant 5R01 AR042429 (to R.D.G. and J.W.), a grant from the Dana Foundation, a gift from the Jacob L. and Lillian Holtzmann Foundation, a grant from the Edith C. Blum Foundation, contributions from the Carl and Fay Simons Family Trust and contributions from the Ann L. and Herbert J. Siegel Philanthropic Fund. ![]()
2 Address correspondence and reprint requests to Dr. Richard D. Granstein, Department of Dermatology, Weill Cornell Medical College, 1305 York Avenue, 9th Floor, New York, NY 10021. E-mail address: rdgranst{at}med.cornell.edu ![]()
3 Abbreviations used in this paper: LC, Langerhans cell; CGRP, calcitonin gene-related peptide; KLH, keyhole limpet hemocyanin; cOVA, chicken OVA; EC, epidermal cell; eEC, LC-enriched EC; pLC, purified LC; CRLR, calcitonin receptor-like receptor; CRCP, CGRP-receptor component protein; Tg, transgenic; CM, complete medium. ![]()
Received for publication February 26, 2008. Accepted for publication September 3, 2008.
| References |
|---|
|
|
|---|
S: purinergic agonists define a novel class of immunologic adjuvants. J. Immunol. 174: 7725-7731.
-calcitonin gene-related peptide. J. Bone Miner. Res. 19: 2049-2056. [Medline]
and IL-4 and downregulated by IFN-
. Cytokine 23: 126-132. [Medline]
β T-cell-receptor transgenic system. Proc. Natl. Acad. Sci. USA 89: 6065-6069.
| |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |