title: Expression and function of a 90-kilodalton homodimeric molecule (10D1 antigen) on human thymocytes.
abstract: The 10D1 Ag is a 90-kDa homodimeric molecule specifically expressed on a subpopulation of human T cells, and is involved in an alternative pathway of T cell activation. In the present study, we have examined the expression and function of the 10D1 Ag on human thymocytes. Three-color FMF analysis showed that the 10D1 Ag was highly expressed on minor but distinct subpopulations of double-negative and CD4 single-positive thymocytes, and weakly on a part of double-positive thymocytes, but not on CD8 single-positive thymocytes. In double-negative thymocytes, the vast majority of 10D1+ cells were immature thymocytes of CD7+2+3- phenotype. Interestingly, 10D1 mAb could induce the proliferation of CD4 single-positive thymocytes in the presence of goat anti-mouse Ig to cross-link the 10D1 Ag. The treatment of thymocytes with OKT4 mAb plus C but not with OKT8 mAb plus C totally abrogated the proliferative response induced by 10D1 mAb, indicating that the 10D1-responsible thymocytes were of CD4+8- phenotype. This 10D1 mAb-induced thymocyte proliferation was perfectly dependent on the endogenous IL-2/IL-2R system since a complete inhibition was observed with anti-IL-2 and anti-IL-2R mAb. The proliferating CD4 single positive thymocytes predominantly expressed the IL-2R alpha (p55) but not a detectable level of the IL-2R beta (p75). These results indicate that, although the 10D1 Ag can be detected on the CD7+2+3-4-8- thymocytes, its functional expression is restricted to a minor more mature CD4+ thymocyte population as well as in peripheral blood T cells, and the implications of these findings are discussed.
authors.affiliation: Department of Immunology, Juntendo University School of Medicine, Tokyo, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Kobata
authors.forename: H
authors.initials: H
authors.lastname: Yagita
authors.forename: H
authors.initials: H
authors.lastname: Matsuda
authors.forename: M
authors.initials: M
authors.lastname: Seki
authors.forename: Y
authors.initials: Y
authors.lastname: Ota
authors.forename: M
authors.initials: M
authors.lastname: Katagiri
authors.forename: K
authors.initials: K
authors.lastname: Okumura
mesh_terms: D000911:Antibodies, Monoclonal / Q000276:immunology; D015703:Antigens, CD / Q000032:analysis; D000954:Antigens, Surface / Q000032:analysis*; D002648:Child; D002675:Child, Preschool; D006801:Humans; D007223:Infant; D007376:Interleukin-2 / Q000502:physiology; D008213:Lymphocyte Activation; D011948:Receptors, Antigen, T-Cell / Q000502:physiology; D015375:Receptors, Interleukin-2 / Q000502:physiology; D013601:T-Lymphocytes / Q000276:immunology*
chemical_list: D000911:Antibodies, Monoclonal; D015703:Antigens, CD; D000954:Antigens, Surface; D007376:Interleukin-2; D011948:Receptors, Antigen, T-Cell; D015375:Receptors, Interleukin-2