Alloreactive cytotoxic T lymphocyte responses to H-2 products on purified accessory cells.

Several purified accessory cell populations were examined for their capacity to stimulate allospecific cytotoxic T lymphocytes (CTL). A number of non-lymphoid accessory cells stimulated CTL directed against the whole H-2 region and to isolated Class I or Class II products of the major histocompatibility complex (MHC). The accessory cells which stimulated CTL expressed surface Ia. The generation of CTL to Class I MHC products could be inhibited by antisera directed at Class II molecules on the same accessory stimulator cell surface. These findings demonstrate the importance of Class II MHC products on heterogeneous accessory cells capable of stimulating alloreactive CTL.