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* Cell Biology and Genetics Program,
Biochemistry and Structural Biology Program, and
Immunology Program, Weill Graduate School of Medical Sciences of Cornell University, New York, NY 10021; and
Sloan-Kettering Institute, Memorial Sloan-Kettering Cancer Center, Immunology Program, New York, NY 10021
In the endosomes of APCs, the MHC class II-like molecule H2-M catalyzes the exchange of class II-associated invariant chain peptides (CLIP) for antigenic peptides. H2-O is another class II-like molecule that modulates the peptide exchange activity of H2-M. Although the expression pattern of H2-O in mice has not been fully evaluated, H2-O is expressed by thymic epithelial cells, B cells, and dendritic cells (DCs). In this study, we investigated H2-O, H2-M, and I-Ab-CLIP expression patterns in B cell subsets during B cell development and activation. H2-O was first detected in the transitional 1 B cell subset and high levels were maintained in marginal zone and follicular B cells. H2-O levels were down-regulated specifically in germinal center B cells. Unexpectedly, we found that mouse B cells may have a pool of H2-O that is not associated with H2-M. Additionally, we further evaluate H2-O and H2-M interactions in mouse DCs, as well as H2-O expression in bone marrow-derived DCs. We also evaluated H2-O, H2-M, I-Ab, and I-Ab-CLIP expression in splenic DC subsets, in which H2-O expression levels varied among the splenic DC subsets. Although it has previously been shown that H2-O modifies the peptide repertoire, H2-O expression did not alter DC presentation of a number of endogenous and exogenous Ags. Our further characterization of H2-O expression in DCs, as well as the identification of a potential free pool of H2-O in mouse splenic B cells, suggest that H2-O may have a yet to be elucidated role in immune responses.
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1 This work was supported by Public Health Service Grants AI46202 and AI61484 (to L.K.D.) and P30-CA08748 (to Memorial Sloan-Kettering Cancer Center).
2 Address correspondence and reprint requests to Dr. Lisa K. Denzin, Sloan-Kettering Institute for Cancer Research, 1275 York Avenue, Box 509, New York, NY 10021. E-mail address: denzinl{at}mskcc.org
3 Abbreviations used in this paper: ER, endoplasmic reticulum; I, invariant; MIIC, MHC class II compartment; CLIP, class II-associated invariant chain peptide; DC, dendritic cell; FO, follicular; MZ, marginal zone; GC, germinal center; sDC, splenic DC; bmDC, bone marrow-derived DC; NP, (4-hydroxy-3-nitrophenyl)acetyl; CGG, chicken 
globulin; IP, immunoprecipitation; PVDF, polyvinylidene difluoride; 
2m, 2-microglobulin; HEL, hen egg lysozyme; SIGN, specific ICAM-3-grabbing nonintegrin; MFI, mean fluorescence intensity; KO, knockout.
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  C. H. Rinderknecht, M. P. Belmares, T. L. W. Catanzarite, A. J. Bankovich, T. H. Holmes, K. C. Garcia, N. K. Nanda, R. Busch, S. Kovats, and E. D. Mellins Posttranslational Regulation of I-Ed by Affinity for CLIP J. Immunol., November 1, 2007; 179(9): 5907 - 5915. [Abstract] [Full Text] [PDF]
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