| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
,
,
Departments of
*
Immunobiology and
Cell Biology,
Ludwig Institute for Cancer Research, Yale University School of Medicine, New Haven, CT 06520; and
Third Medical Department, Technical University of Munich, Klinikum rechts der Isar, Munich, Germany
 |
Abstract |
|---|
 Top Abstract IntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
|
Introduction |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
Upon peptide/MHC class II recognition, signaling, adhesion, and cytoskeletal (4, 7) molecules in T cells are concentrated at the site of contact with an APC. The organization at the contact site involves both an enrichment of specific proteins and a depletion of others, resulting in a highly specific arrangement of the aggregated proteins within the immunological synapse (3, 4). Lipid microdomains are thought to play an important role in the localization of signaling proteins to the synapse (8, 9). During T cell activation, the TCR, its coreceptor CD4, and the Src kinases Lck and Fyn are recruited to these microdomains (10, 11, 12, 13, 14). Costimulatory signals then mediate raft aggregation to the site of synapse (15). These molecular rearrangements at the synapse have been defined from the T cell point of view using anti-CD3 coated beads (15), B cell lines (3, 16), or lipid bilayers (17) to present Ag.
The organization of proteins on the APC side of an immunological synapse is less well defined. Similar to T cells, the BCR has been reported to be recruited to lipid rafts and clustered at the synapse site (18, 19, 20). Recently, it has been shown that B cells constitutively localize at least a fraction of their MHC class II molecules in lipid rafts (21), suggesting that lipid rafts have a functional role in B cells in Ag presentation. However, the role of lipid rafts in recruiting proteins and promoting their aggregation at the immunological synapse has not been investigated in DCs.
In this study we ask whether the key counter-receptors essential for T cell activation (MHC class II and CD86) show a similar pattern of raft recruitment and polarization to the immunological synapse in DCs as that seen in T cells. We show that both MHC class II and CD86 are recruited to lipid rafts, but the mechanism of recruitment differs between the two. MHC class II molecules are associated with lipid rafts upon maturation, during which time CD86 is excluded from lipid microdomains. However, CD86 is recruited to lipid rafts upon T cell-DC interaction. Despite these events and in contrast to T cell clustering of TCR and CD28 molecules, DCs do not greatly enrich their MHC class II and CD86 molecules at the DC-T cell contact site.
|
Materials and Methods |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
AND-transgenic mice, in which CD4+ T cells express a TCR specific for moth cytochrome c peptide (MCC) in the context of I-Eb or I-Ek, have been previously described (22). These mice were bred in our facilities and maintained as heterozygotes on a C57BL/6 (B6) and B10.BR background. 3A9 TCR transgenic were also bred in our facility. CD28–/– mice were originally on a C57BL/6 background and were crossed with AND TCR and transgenic mice on the C57BL/6 background. DO11.10 transgenic mice for the OVA (OVA 323–339)-specific (H-2d) TCR were also bred in our facility and on the BALB/c background. C57BL/6 and BALB/c mice were obtained from the National Cancer Institute (Bethesda, MD), and C3H/HeJ mice were obtained from The Jackson Laboratory (Bar Harbor, ME). All mice used in these studies were 5–10 wk old.
Antibodies
The following mAbs were used in this study: anti-CD4 (GK1.5), anti-CD8 (TIB 210), anti-Thy-1 (Y19), anti-NK (HB191), anti-MHC class II (212.A1, TIB 93, TIB 120 (23), and 14.4.4), anti-CD32/16 (2.4G2), anti-B220 (TIB 164), and anti-CD40. All Abs were purified from culture supernatants on protein G columns and dialyzed against PBS before use. Polyclonal anti-I-Aa was a gift from M. Marks (University of Pennsylvania, Philadelphia, PA). mAbs were as purchased as follows: anti-CD86 (Santa Cruz Biotechnology, Santa Cruz, CA); anti-phosphoserine (Calbiochem, San Diego, CA); anti-phosphotyrosine (Upstate Biotechnology, Lake Placid, NY); and anti-MHC class II (2G9), anti-CD3e (2C11), and anti-CD86 (GL1) (BD Pharmingen, San Diego, CA). HRP-conjugated cholera toxin subunit was purchased from Sigma-Aldrich (St. Louis, MO); FITC-conjugated cholera toxin was purchased from List Biological Laboratories (Campbell, CA). The following fluorescent secondary Abs were purchased from Molecular Probes (Eugene, OR): Alexa 488 anti-FITC, Alexa 488 goat anti-mouse, Alexa 488 goat anti-rabbit, Alexa 647 rabbit anti-goat, Alexa 594-streptavidin, Alexa 568 goat anti-rabbit, Alexa 568 goat anti-rat, and Alexa 488 goat anti-rat. Goat anti-mouse Cy5 and goat anti-Armenian hamster Cy5 were purchased from Jackson ImmunoResearch Laboratories (West Grove, PA).
Generation of DCs
Bone marrow-derived DCs were generated as previously described (24). In brief, bone marrow cells were cultured in the presence of 1% culture supernatant from a cell line transfected with the murine GM-CSF gene (25) for 10 days. After 10 days, these immature DCs were harvested and stimulated with 30 ng/ml LPS (Sigma-Aldrich). On day 11, mature DCs were analyzed by FACS and used as indicated.
Peptides
MCC (peptide 88–103; pMCC = VFAGLKKANERADLIAYLKQATK) and OVA (peptide 323–339; pOVA = ISQAVHAAHAEINAEGR) were synthesized by the W. M. Keck Foundation Biotechnology Resource Laboratory (New Haven, CT).
Preparation of CD4+ T cells
CD4+ and CD8– T cells from lymph nodes and spleens of the mice mentioned above were isolated by immunomagnetic negative selection as previously described (26) using Abs against CD8, CD32/CD16, B220, MHC class II, and NK cells, followed by incubation with anti-mouse and anti-rat Ig-coated magnetic beads (Polysciences, Warrington, PA). The purity of the recovered CD4+ T cells was usually 85–95%, as determined by staining with anti-CD4 and anti-TCR.
Membrane biotinylation
Immature or mature DCs were washed three times with PBS and incubated with 1 mg/ml sulfo-NHS-biotin (Pierce, Rockford, IL) for 30 min on ice. Cells were then washed with PBS and lysed, and raft fractions were isolated as described.
Ab cross-linking
DCs (15 x 106) were incubated with 5 µg/ml anti-CD86 mAb, anti-CD40 mAb, or anti-MHC II mAb or without mAb on ice for 30 min. After washing, the Abs were cross-linked with 2 µg/ml goat anti-rat F(ab)2 at 37°C for 15 min. Cells were lysed in ice-cold lysis buffer, and raft fractions were isolated as described.
Purification of raft fractions
Rafts were prepared by cell lysis, followed by sucrose gradient fractionation as previously described (27). Four-hundred-microliter fractions were collected from the top of the gradient. The protein concentration of each fraction was determined using the Bio-Rad (Hercules, CA) protein assay kit, which is based on the Bradford dye-binding procedure. Fractions were pooled or analyzed individually by SDS-PAGE and Western blotting.
Immunoprecipitation and Western blotting
For immunoprecipitations of biotinylated surface molecules streptavidin-agarose beads were used (Upstate Biotechnology) and incubated with the lysates for an additional 1 h at 4°C. Western blot analysis was performed using the indicated Abs after SDS-PAGE and transfer onto nitrocellulose paper (Schleicher & Schuell, Keene, NH). All immunoblots were developed with the ECL chemiluminescent system (Amersham Biosciences, Arlington Heights, IL). Where indicated, Western blots were quantitated by densitometric scanning.
Ag presentation
Mature DCs were pulsed with various doses of OVA peptide or without peptide as indicated. After pulsing, DC’s were treated with 75 mg/ml Nystatin (Sigma-Aldrich) and fixed with 0.7% paraformaldehyde (PFA). Naive DO.11+ CD4 T cells were cultured at 200,000 cells/well in 96-well, flat-bottom tissue culture plates (Costar, Cambridge, MA) with 5,000 mature DCs in Bruff’s high amino acid medium supplemented with 10% FCS, 50 U/ml penicillin, 50 µg/ml streptomycin sulfate, and 10 mM HEPES. Culture supernatants were collected after 48 h, and IL-2 was quantified using an IL-2 ELISA minikit (R&D Systems, Minneapolis, MN).
Immunofluorescence microscopy
DCs were analyzed alone or mixed with CD4+ T cells for 10 min at 37°C. T cell-DC conjugates were then placed on Alcian Blue-coated coverslips in serum-free medium and incubated for 20 min at 37°C to permit adherence. Cells were fixed in 4% PFA in PBS, then stained in staining buffer (10% goat serum, 0.05% saponin, 10 mM HEPES, and 10 mM glycine). Ab incubations were performed as previously described (28) using the indicated Abs. Coverslips were mounted in ProLong mounting medium (Molecular Probes, Eugene, OR), and fluorescence patterns were analyzed using a Zeiss LSM 510 confocal microscope (Oberkochen, Germany) equipped with a x40 (1.4NA Plan Apochromat) water immersion lens. Acquisition was performed using Zeiss LSM 510 (version 3.0) software, and processing was completed using Photoshop 7.0 (Adobe Systems, San Jose, CA).
|
Results |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
As B cells constitutively express at least a fraction of their MHC class II molecules in lipid rafts (21), we asked whether MHC class II molecules are similarly associated with lipid rafts in DCs, and whether this association was regulated by the DCs. We approached this by isolating lipid rafts from bone marrow-derived immature and mature DCs by sucrose gradient centrifugation and analyzing the raft (fractions 1–4) and nonraft fractions (fractions 7–10) for the presence of MHC class II molecules. As expected, the raft-associated lipid, GM-1 ganglioside was highly enriched in lipid rafts (fractions 1–4; Fig. 1A, panel 1). As shown in Fig. 1A, (panel 3), MHC class II molecules were partly localized in lipid rafts in mature DCs. By contrast, little, if any, MHC class II was associated with lipid rafts in immature DCs (Fig. 1A, panel 2). We next investigated the lipid raft distribution of the surface MHC class II pool. To determine the fraction of surface MHC class II molecules that was associated with lipid rafts, cell surface proteins from mature DCs were selectively labeled with sulfo-NHS biotin. Biotinylated proteins were isolated from lysates with streptavidin-agarose beads, and MHC class II expression in raft and nonraft fractions was determined by Western blotting. As shown in Fig. 1A (panel 4), there was a significant portion of cell surface MHC class II molecules associated with lipid rafts. Quantitative densitometry of the immunoblots revealed that 
66% of the surface MHC class II molecules of mature DCs were localized in lipid rafts (Fig. 1B). In contrast, little, if any, surface MHC class II could be detected in immature DCs (data not shown). This demonstrates that during DC maturation, MHC class II molecules not only increased in overall surface expression, but also become specifically recruited to lipid rafts.
|
Naive T cells require both recognition of peptide/MHC class II complexes as well as costimulatory signals to become fully activated. Because MHC class II become lipid raft-associated during maturation (Fig. 1), we asked whether CD86 is also associated with lipid rafts in mature DCs. To test this, lipid raft fractions were isolated from immature and mature DCs. In contrast to MHC class II molecules, CD86 was not raft-associated in either immature or mature DCs (Fig. 2, panels 2 and 3), although the total amount of CD86 was, as expected, much higher in mature DCs than in immature DCs. To determine whether CD86 was recruited to lipid rafts upon ligation, we cross-linked CD86 with anti-CD86 Ab on mature DCs and analyzed its distribution to lipid rafts. As shown in Fig. 2 (panel 4), cross-linking of CD86 resulted in its recruitment to lipid rafts. This association was not seen after ligation with anti-MHC class II Ab (Fig. 2, panel 5). Interestingly, we also detected CD86 recruitment to lipid rafts after CD40 ligation, although to a lesser extent (Fig. 2, panel 6). These data suggest that the recruitment of CD86 to lipid rafts is a specific, inducible event.
|
As the recruitment of CD86 to lipid rafts is a highly regulated event, we questioned whether raft-associated CD86 influences the activation of mature DCs. DCs were stimulated with anti-CD86, anti-MHC class II, or anti-CD40 Abs. After lysis and sucrose ultracentrifugation, raft fractions 1–4 and nonraft fractions 7–10 were pooled and separated by SDS-PAGE. Immunoblotting was performed with phosphotyrosine (not shown) and phosphoserine-specific Abs. Phosphorylated serines could be observed in both raft and nonraft fractions (Fig. 3). However, there was an inducible phosphoserine pattern seen in the raft fractions after anti-CD86 as well as anti-CD40 ligation (Fig. 3A). Interestingly, the phosphotyrosine pattern was not significantly changed after anti-CD86, anti-MHC class II, or anti-CD40 stimulation in either raft or nonraft fractions (data not shown). These data indicate that ligation of CD86 and CD40, but not MHC class II, leads to the recruitment of serine-phosphorylated proteins to lipid rafts. Furthermore, it suggests a specific function of raft-associated CD86 in DC.
|
To determine whether CD86 becomes recruited to lipid rafts under more physiological conditions, we analyzed CD86 association with lipid rafts during T cell activation by peptide-loaded DCs. We stimulated mature DCs that were pulsed with moth cytochrome c peptide (MCC) with AND TCR-transgenic CD4+ T cells from either wild-type or CD28–/– mice. After 20 min of activation, cells were lysed, and raft fractions were prepared. As shown in Fig. 4 (panel 3), CD86 was recruited to lipid rafts upon T cell activation. This recruitment of CD86 required CD28 ligation, in that there was no redistribution of CD86 to lipid rafts upon conjugation with CD28–/– T cells (Fig. 4, panel 4). Furthermore, this recruitment of CD86 was Ag dependent, requiring T cell activation, in that unpulsed DCs did not support CD86 raft association (Fig. 4, panel 2). The fact that we did not see CD86 recruitment to lipid rafts by MHC class II ligation (Fig. 2) is consistent with the fact that Ag alone in the absence of CD28 is not sufficient to recruit CD86 to lipid rafts. These data indicate that the CD28-CD86 interaction not only influences T cell signaling, but may also affect signaling in DCs, given the recruitment of CD86 to lipid rafts.
|
Ag-specific interactions of T cells with APCs often result in the accumulation of lipid raft components at the intercellular contact site or synapse (29, 30). Given the constitutive or induced localization of MHC class II and CD86 to lipid microdomains in DCs, we next determined whether these molecules also polarized to contact sites upon T cell interaction. To test this possibility, peptide or protein-pulsed DCs were cultured with naive CD4+ 3A9 primary T cells for 20 min. The resulting T cell-DC conjugates were analyzed for total MHC class II, CD86, and CD3
distribution by confocal microscopy. As shown in Fig. 5, neither MHC class II nor CD86 clustering was observable at sites of T cell contact, regardless of whether the DCs were pulsed with peptide (Fig. 5a) or protein (Fig. 5b). The lack of clustering was evident both at low resolution (Fig. 5, left panels, three-color merged images) or upon magnification of individual contact sites (Fig. 5, boxed areas, with each marker displayed as single colors). Even at contact sites where the bound T cells exhibited a clear clustering of the TCR (CD3; Fig. 5, arrows; 10% of all such contacts), a corresponding polarization of MHC class II and CD86 was not observed. The lack of clustering was not due to poor accessibility of MHC class II to added Abs, because the same results were obtained using multiple reagents, including Abs to the MHC class II 
-chain cytoplasmic tail (data not shown). TCR polarization occurred even using CD28-deficient T cells, suggesting that the localization of CD86 to contact sites was not required to elicit CD3 polarization (Fig. 5c).
|
We also monitored the distribution of GM1 gangliosides, a glycolipid component of many lipid rafts, by labeling with cholera toxin B. Again, clustering of cholera toxin to contact sites was not seen (not shown), although this result indicated only that there was not a bulk rearrangement of all GM1 molecules upon T cell engagement.
Taken together, these results indicate that despite the fact that DCs recruited the molecules necessary for Ag presentation to lipid rafts upon T cell engagement, they did not visibly cluster the raft-associated MHC class II and CD86 at the contact sites. Indeed, the differential responses of T cells and DCs to forming contacts was further emphasized by the different behaviors of the microtubule networks in both cells. As shown previously, microtubules in T cells polarized toward sites of interaction with DCs (Fig. 5d). On the DC side, however, no such reorientation was noted (Fig. 5e). Regardless of whether the DCs were viewed as single confocal or three-dimensional reconstructions, the microtubule network appeared distributed equivalently among dendrites that were or were not in contact with T cells.
Cholesterol depletion inhibits Ag presentation by DCs
Given that DCs did not selectively redistribute their lipid raft components to sites of T cell contact, we next asked whether these membrane microdomains were functionally relevant to Ag presentation. For this purpose, we investigated the effect of Nystatin on T cell priming. Nystatin is a polyene antifungal agent that disrupts cholesterol-rich membrane domains (21). To disrupt lipid rafts, peptide-loaded DCs were incubated for 45 min with Nystatin. To prevent reassembly, cells were fixed after raft disruption and then used as APCs. As shown in Fig. 6, disruption of lipid rafts with Nystatin led to a decrease in T cell activation. Measuring the amount of IL-2 that has been secreted into the culture supernatant after 48 h, there was a significant decrease at both high and low Ag concentrations. At the lower Ag concentration, Nystatin treatment resulted in a 4-fold decrease in IL-2 production, whereas at the higher Ag concentration the decrease was 2-fold. The effect of raft disruption was also confirmed using protein-loaded DCs as APC (data not shown). The Nystatin treatment was not toxic, because the raft disruption was reversible, as demonstrated using DCs that were rested in medium without Nystatin for 1 h before fixing the cells (data not shown). Although treatment with agents such as Nystatin might have multiple effects on DCs, it is known to disrupt lipid rafts; therefore, these results are consistent with a functional role for rafts in T cell stimulation by DCs.
|
|
Discussion |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
In a first step, MHC class II molecules are recruited to lipid rafts upon DC maturation. Whereas immature DCs exhibit little, if any, MHC class II in rafts, mature DCs have about two-thirds of their surface MHC class II pool localized to these microdomains. DC maturation by itself does not lead to CD86 raft association, but, rather, requires a second step, namely, T cell interaction. The DC is therefore different from B cells in this regard. B cells exhibit a constitutive expression of MHC class II in lipid rafts (21), whereas, at least in B cell lymphomas, CD86 may actually be excluded (30). Finally, as shown in B cells (21), the raft association of Ag presentation molecules leads to an effective T cell priming, as disruption of rafts in DCs diminished the IL-2 production of activated T cells.
What is the mechanism of regulated CD86 recruitment? It has long been known, particularly in the case of GPI-anchored membrane proteins, that physical cross-linking can result in raft recruitment (31). Although CD86 is an authentic type I membrane protein, Ab cross-linking nevertheless induced its recruitment to lipid rafts on DCs. It seems likely, therefore, that interaction with T cells results in CD86 recruitment due to a physical cross-linking of CD86 by its cognate ligand, CD28. Indeed, T cells from CD28–/– mice were unable to trigger CD86 relocalization to rafts, even though these T cells were themselves able to respond productively to DC interaction (CD3 polarization).
These data demonstrate the bidirectional interaction between CD28 on a T cell and CD86 on the DC. Naive CD4 T cells receive their costimulatory signal during this interaction, and the DCs appear to respond by reorganizing their CD86 to lipid rafts. Although the functional significance of the CD86 response remains to be determined, the fact that the ligation and recruitment of CD86 to lipid rafts is required for the appearance of phosphorylated serines in rafts, supports the idea that this is a mutually beneficial interaction that modulates not only T cell, but also DC, signaling. After CD40 ligation, we saw a similar serine phosphorylation pattern. Because CD40 ligation has been shown to send an antiapoptotic signal to DCs (32, 33), it might be speculated that there is a similar function for CD86. The fact that signaling through CD86 enhances the expression of antiapoptotic molecules in B cells supports this idea (34). Indeed, our data show that CD86 ligation leads to an antiapoptotic signal that prolongs the life span of DCs both in vitro and in vivo (C. Meyer zum Bueschenfelde, J. L. Brogdan, I. Visintin, I. Mellman, and K. Bottomly, manuscript in preparation). Currently, we are investigating whether CD86 recruitment to rafts is necessary for signaling and which signaling events in DCs promote CD86 recruitment to rafts.
In contrast to T cells, we did not observe a clear clustering of membrane proteins (MHC class II and CD86) or lipids (GM1) in DCs at T cell contact sites. This is in contrast to previous work in which MHC class II molecules have been found to cluster at the T cell-APC contact site. However, none of these studies used primary DCs as APC (30, 35, 36). One possible explanation for the differences seen is that clustering of MHC class II and CD86 might not be detected microscopically in primary DCs due to their comparatively high levels of expression of MHC and costimulatory molecules. Thus, there may be insufficient TCR on the interacting T cells to elicit a detectable accumulation of MHC class II at the synapse. Cognate peptide-MHC complexes, in contrast, may be seen to cluster slightly when allowed to interact with Ag-specific T cells (J. Unternaehrer, manuscript in preparation) (36). DCs also differ from B cells in their ability to form lateral arrays of MHC class II, possibly stabilized by tetraspanins (J. Unternaehrer, A. Chow, M. Pypaert, K. Inaba, R. M. Steinman, and I. Mellman, manuscript in preparation).
We also cannot rule out the possibility that microclusters on the DC surface localize to contact sites, causing clustering that is simply not discernable by confocal microscopy. In this respect, it is important to emphasize that lipid rafts themselves are exceedingly small (<5 nm), well below the limit of resolution of light microscopy (37). Thus, the fact that DC maturation combined with T cell interaction causes a dramatic recruitment of MHC class II and CD86 to lipid rafts defined biochemically (on density gradients) does not mean that there must be a morphologically identifiable correlate for this event (37).
It may seem surprising that perhaps the most professional of all APCs, the DC, fails to efficiently cluster its MHC class II and CD86 at sites of T cell interaction. However, were they to do so, the DC’s efficiency might actually be diminished. It is known that CD4+ T cells respond with transient calcium signaling to even a single agonist peptide MHC class II ligand (38). Furthermore, synapse formation could be initiated with as few as 10 agonist peptide/MHC class II complexes present (38). Thus, even from the T cell’s point of view, it might not be necessary for DCs to reorganize their surface proteins to induce clustering of essential signaling and recognition molecules. The already high density of MHC class II and CD86 on the cell surface of mature DCs combined with the raft association of MHC class II and CD86 may further enhance the opportunities for T cell activation by creating microclusters of TCR ligand and costimulatory molecules with even higher local density. By obviating the need to polarize its components toward interacting T cells, the DC can maintain a highly dynamic organization of its plasma membrane, enabling simultaneous Ag presentation to multiple T cells, as observed both in vitro and in vivo.
|
Footnotes |
|---|
1 This work was supported by grants from the National Institutes of Health (R01CA38350-23 and R37AI26791-16 (to K.B.) and R37-AI34098 (to I.M.)) and the Ludwig Institute for Cancer Research (I.M.) and Deutsche Forschungsgemeinschaft (to C. M.z.B.). 
2 Address correspondence and reprint requests to Dr. Christian O. Meyer zum Bueschenfelde, Department of Hematology, Technical University of Munich, Ismaninger Strasse 22, 81675 Munich, Germany. E-mail address: christian.mzb{at}lrz.tum.de
3 Abbreviations used in this paper: DC, dendritic cell; MCC, moth cytochrome c; PFA, paraformaldehyde.
Received for publication June 3, 2004. Accepted for publication August 29, 2004.
|
References |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
This article has been cited by other articles:
|
|
 |
|
  R. Knorr, C. Karacsonyi, and R. Lindner Endocytosis of MHC molecules by distinct membrane rafts J. Cell Sci., May 15, 2009; 122(10): 1584 - 1594. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 C. Ocana-Morgner, C. Wahren, and R. Jessberger SWAP-70 regulates RhoA/RhoB-dependent MHCII surface localization in dendritic cells Blood, February 12, 2009; 113(7): 1474 - 1482. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 C. Gelin, I. Sloma, D. Charron, and N. Mooney Regulation of MHC II and CD1 antigen presentation: from ubiquity to security J. Leukoc. Biol., February 1, 2009; 85(2): 215 - 224. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
T. L. Herrmann, R. S. Agrawal, S. F. Connolly, R. L. McCaffrey, J. Schlomann, and D. J. Kusner MHC Class II levels and intracellular localization in human dendritic cells are regulated by calmodulin kinase II J. Leukoc. Biol., September 1, 2007; 82(3): 686 - 699. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 N. W. Kin and V. M. Sanders CD86 Regulates IgG1 Production via a CD19-Dependent Mechanism J. Immunol., August 1, 2007; 179(3): 1516 - 1523. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
R. P. Jackman, F. Balamuth, and K. Bottomly CTLA-4 Differentially Regulates the Immunological Synapse in CD4 T Cell Subsets J. Immunol., May 1, 2007; 178(9): 5543 - 5551. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 J. J. Unternaehrer, A. Chow, M. Pypaert, K. Inaba, and I. Mellman The tetraspanin CD9 mediates lateral association of MHC class II molecules on the dendritic cell surface PNAS, January 2, 2007; 104(1): 234 - 239. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
B. Kovacs, R. V. Parry, Z. Ma, E. Fan, D. K. Shivers, B. A. Freiberg, A. K. Thomas, R. Rutherford, C. A. Rumbley, J. L. Riley, et al. Ligation of CD28 by Its Natural Ligand CD86 in the Absence of TCR Stimulation Induces Lipid Raft Polarization in Human CD4 T Cells J. Immunol., December 15, 2005; 175(12): 7848 - 7854. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
C. Karacsonyi, T. Bedke, N. Hinrichsen, R. Schwinzer, and R. Lindner MHC II molecules and invariant chain reside in membranes distinct from conventional lipid rafts J. Leukoc. Biol., November 1, 2005; 78(5): 1097 - 1105. [Abstract] [Full Text] [PDF]
|
|
| |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
