CD8 T cells from major histocompatibility complex class II-deficient mice respond vigorously to class II molecules in a primary mixed lymphocyte reaction.
Mature CD4+ and CD8+ T cells are restricted by major histocompatibility complex (MHC) class II and class I molecules, respectively. In a primary mixed lymphocyte reaction (MLR), CD8+ T cells from C57BL/6 (B6) mice can respond to allo-class I molecules, but not allo-class II molecules. However, a significant fraction of CD8+ T cells from C57BL/6 class II-deficient (B6Aalpha-) mice violate this rule by responding vigorously in a MLR to class II molecules. The frequency of responding cells is approximately 50% of that of B6 CD8+ T cells responding to B6bm1 allo-class I molecules. This response requires neither appropriate co-receptor, i.e. CD4, nor exogenous lymphokines, indicating that interactions between the T cell receptors (TCR) and class II molecules are remarkably efficient. Since these CD8+ T cells are positively selected by class I molecules in the thymus of class II-deficient mice, these CD8+ T cells should interact with both classes of MHC molecules. The absence of thymic negative selection by class II molecules may result in the production of these CD8+ T cells. The data imply that a substantial fraction of CD4+CD8+ double-positive thymocytes in wild-type mice interacts with both classes of MHC molecules prior to thymic selection.
Shimizu
T
T
Basel Institute for Immunology, Switzerland.
Takeda
S
S
D000818:Animals; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology*; D000949:Histocompatibility Antigens Class II / Q000235:genetics* / Q000276:immunology*; D008213:Lymphocyte Activation / Q000276:immunology*; D007959:Lymphocyte Culture Test, Mixed; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D001613:beta 2-Microglobulin / Q000172:deficiency / Q000235:genetics
D000949:Histocompatibility Antigens Class II; D001613:beta 2-Microglobulin