Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P06126 (CD1a)
 2,221 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The CD1 family of proteins are structurally related to MHC class I proteins, but are only distantly related to the class I proteins or other MHC-linked class I-like proteins. Sequence comparisons indicate that the CD1 proteins have evolved into two subfamilies, those which are similar to human CD1a, b, and c and those which are similar to human CD1d. The CD1A-, B-, and C-like genes were deleted from rodents and the CD1D gene was duplicated. CD1a, b, and c are expressed by thymocytes, dendritic cells, activated monocytes, and B cells (CD1c), a tissue distribution which strongly suggests a role in antigen presentation. In contrast, CD1d and its murine homologues are expressed by many cells outside of the lymphoid and myeloid lineages. The CD1 proteins are in most cases expressed as beta 2mg-associated membrane glycoproteins, but may associate with additional proteins. CD1d is expressed on the surface of intestinal epithelial cells in a nonglycosylvated form without beta 2mg. Whether the CD1 proteins function as antigen-presenting molecules is unresolved, but it is unlikely that they present conventional peptide antigens. Strong evidence indicates that murine CD1 proteins are recognized by a population of NK1.1+, CD4+ or CD4-CD8- (double negative, DN) T cells which express an invariant TCR alpha chain. CD1d is most likely recognized by the homologous T cell population in humans. DN alpha beta T cells which recognize CD1a, b, or c have been isolated, including clones which recognize a lipid antigen from mycobacteria presented by CD1b. A third potential population of CD1 reactive cells are CD8+ T cells in the intestinal epithelium. Taken together, these observations indicate that CD1 proteins interact with several specialized populations of T cells. The precise biological functions mediated through these interactions remain to be determined.
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PMID:Structure and function of the CD1 family of MHC-like cell surface proteins. 884 79

The presentation of lipid and glycolipid Ags to T cells is mediated through CD1 molecules. In the mouse and rat only a single isoform, CD1d, performs these functions, while humans and all other mammals studied have members of both group I (CD1a, -b, and -c) and group II (CD1d) isoforms. Murine CD1d contains a cytoplasmic tyrosine-based sorting motif that is similar to motifs recognized by adaptor protein complexes that sort transmembrane proteins. Here we show that the adaptor protein complex, AP-3, directly interacts with murine CD1d and controls its targeting to lysosomes. AP-3 deficiency results in a redistribution of CD1d from lysosomes to the cell surface of thymocytes, B cell-depleted splenocytes, and dendritic cells. The altered trafficking of CD1d in AP-3-deficient mice results in a significant reduction of NK1.1(+)TCR-beta(+) and CD1d tetramer-positive cells, consistent with a defect in CD1d self-Ag presentation and thymocyte-positive selection. The AP-3 complex has recently been shown to associate with the human CD1b isoform, which has an intracellular distribution pattern similar to that of murine CD1d. We propose that lysosomal sampling may be so critical for efficient host defense that mice have evolved mechanisms to target their single CD1 isoform to lysosomes for sampling lipid Ags. Here we show the dominant mechanism for this trafficking is mediated by AP-3.
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PMID:Lysosomal localization of murine CD1d mediated by AP-3 is necessary for NK T cell development. 1453 Mar 37

Group 1 CD1 (CD1a, -b, and -c) presents self and foreign lipid antigens to multiple T-cell subsets in humans. However, in the absence of a suitable animal model, the specific functions and developmental requirements of these T cells remain unknown. To study group 1 CD1-restricted T cells in vivo, we generated double transgenic mice (HJ1Tg/hCD1Tg) that express group 1 CD1 molecules in a similar pattern to that observed in humans (hCD1Tg) as well as a TCR derived from a CD1b-autoreactive T-cell line (HJ1Tg). Using this model, we found that similar to CD1d-restricted NKT cells, HJ1 T cells exhibit an activated phenotype (CD44(hi)CD69(+)CD122(+)) and a subset of HJ1 T cells expresses NK1.1 and is selected by CD1b-expressing hematopoietic cells. HJ1 T cells secrete proinflammatory cytokines in response to stimulation with CD1b-expressing dendritic cells derived from humans as well as hCD1Tg mice, suggesting that they recognize species conserved self-lipid antigen(s). Importantly, this basal autoreactivity is enhanced by TLR-mediated signaling and HJ1 T cells can be activated and confer protection against Listeria infection. Taken together, our data indicate that CD1b-autoreactive T cells, unlike mycobacterial lipid antigen-specific T cells, are innate-like T cells that may contribute to early anti-microbial host defense.
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PMID:Autoreactive CD1b-restricted T cells: a new innate-like T-cell population that contributes to immunity against infection. 2186 21