Widespread expression of the nonclassical class I Qa-2 antigens in hemopoietic and nonhemopoietic cells.
We reexamined expression patterns of one of the best characterized mouse class Ib MHC molecules, Qa-2. Transcripts encoding glycosylphosphatidylinositol-linked and soluble forms of Qa-2 are expressed in all organs except brain. The membrane-bound Qa-2 proteins are detectable, to varying degrees, in many cell types of immunological interest: on professional antigen-presenting cells capable of inducing anti-Qa-2 allogeneic responses, on thymic epithelial cells essential for T-cell positive selection, on mature as well as immature thymocytes, in immunologically privileged sites (testis/spermatazoa), and on cells implicated in mucosal immunity (lymphoid-derived and epithelial gut cells and hepatocytes). Although Qa-2 has a nearly ubiquitous tissue distribution similar to H2-Kb and Db molecules, the relative levels of Qa-2 and class Ia displayed on cell surfaces vary in a cell-specific fashion. Analyses of primary cell lines derived from normal mouse tissues also support the conclusion that Qa-2 is present in all cells that can express class Ia antigens. In contrast, tumor lines from Qa-2-positive mice are frequently Qa-2 deficient, suggesting that the Qa-2-negative phenotype of malignant cells is selected in vivo.
Ungchusri
T
T
Center for Immunology, University of Texas Southwestern Medical Center, 5323 Harry Hines Blvd., Dallas, TX 75390-9093, USA.
Chiang
E Y
EY
Brown
G
G
Chen
M
M
Tabaczewski
P
P
Timares
L
L
Stroynowski
I
I
D000818:Animals; D000938:Antigen-Presenting Cells / Q000276:immunology; D001854:Bone Marrow Cells / Q000276:immunology*; D002460:Cell Line; D022781:Hepatocytes / Q000276:immunology; D015395:Histocompatibility Antigens Class I / Q000096:biosynthesis* / Q000235:genetics; D007413:Intestinal Mucosa / Q000276:immunology; D008297:Male; D051379:Mice; D009369:Neoplasms / Q000378:metabolism; D012333:RNA, Messenger / Q000096:biosynthesis; D013737:Testis / Q000276:immunology; D013950:Thymus Gland / Q000276:immunology; D014018:Tissue Distribution; D014158:Transcription, Genetic; D014407:Tumor Cells, Cultured
D015395:Histocompatibility Antigens Class I; C032907:Q surface antigens; D012333:RNA, Messenger