Influence of the H-2u haplotype on immune function in F1 hybrid mice. II. F1 antiparent mixed lymphocyte reactivity.

Recently we reported that antigen-primed T cells from (H-2u X H-2s) F1 and (H-2u X H-2q)F1 mice responded poorly in vitro to antigen in the context of antigen-presenting cells of the non-H-2u parent. It was suggested that this effect might be due to unbalanced expression of parental antigens in the F1 hybrid with the result that the non-H-2u A antigens were greatly reduced or absent in these mice. If this were the case, non-H-2u Ia-A cells might be expected to stimulate a mixed lymphocyte reaction (MLR) when cultured with F1 responder cells. When tested, (SJL X PL)F1 responder cells reacted strongly to SJL stimulator cells. There was no significant reaction to PL stimulator cells. The use of major histocompatibility complex (MHC) congenic mice showed the stimulatory antigens to be associated with the MHC. The MLR could be blocked significantly by monoclonal A-specific antibody of the appropriate specificity. When a monoclonal antibody reactive with a private epitope associated with As was used to probe for the presence of As on the surface of (SJL X PL)F1 spleen cells, no antigen could be detected, indicating loss or alteration of this antigen. These findings suggest that an alteration of the expression of the parental As molecule may be responsible for this phenomenon.