MECHANISM OF ENHANCED ANTIGEN PRESENTATION BY B-CELLS ACTIVATED WITH ANTI-MU PLUS INTERFERON-GAMMA - ROLE OF B7-2 IN THE ACTIVATION OF NAIVE AND MEMORY CD4(-CELLS() T)

B cells activated with anti-CL antibody plus interferon (IFN)-gamma ex erted strong antigen presentation activity for T cell proliferation. T he enhanced antigen presentation function was shown to be due to the i ncrease in B7-2 expression. When B cells were stimulated with anti-mu, expression of MHC major histocompatibility complex class II, heat-sta ble antigen (HSA), ICAM-1 and B7-2 was increased. The presence of IFN- gamma further augmented the expression of B7-2 on anti-mu-stimulated B cells. B7-1 was not expressed on B cells under these conditions. The participation of B7-2 in the elicitation of the proliferative response of T cells was confirmed by the inclusion of anti-B7-2 antibody in cu ltures. The enhanced expression of either HSA or ICAM-1 was shown not to play a major role in the increased B cell antigen presentation capa city. The major T cell population responding to this activated B cell antigen presentation was shown to be CD44(low) naive CD4(+) T cells, w hereas CD45RB(low) memory CD4(+) Teens responded only weakly The diffe rence in proliferative responses between naive and memory CD4(+) T cel ls was explained by the different efficiency in IL-2 production of the se cell populations in response to antigen presentation by B cells act ivated by anti-mu plus IFN-gamma. These results suggest that IFN-gamma plays an important role in recruitment of naive T cells for an immune response.