Functional expression of HLA-C blank antigens on human blood lymphocytes.

The surface expression of two HLA-C blank Ag (Cb-1 and Cb-2) on PBL was investigated with Cb-1- and Cb-2-specific CTL clones generated by the stimulation of the HLA-C blank Ag on transfected Hmy2CIR cells. The Cb-1- and Cb-2-specific CTL clones could lyse EBV-transformed B cells and PHA-induced T cells from which the HLA-C blank genes were derived. Furthermore, the reactivity of these CTL clones with PHA-induced T cells was blocked by HLA class I monomorphic mAb. These results demonstrated that the HLA-C blank Ag are expressed on the surfaces of PBL. Thus, despite the fact that the HLA-C blank Ag are expressed on normal PBL, they are incapable of generating corresponding alloantibodies. On the other hand, the present study demonstrated that these Ag on normal PBL are able to induce specific CTL and that the capacity of these Ag to induce allogeneic CTL is almost identical to that of HLA-B Ag, indicating that they may function as alloantigens in vivo and play a significant role in the rejection of organ grafts and in the graft-versus-host reaction in bone marrow transplantation.