“B”-cell Stimulation of Allogeneic T-cell Proliferation in Mixed Lymphocyte Cultures

Abstract

CELLULAR immune responses are thought to be mediated by effector cells that result from antigen stimulated proliferation and differentiation of thymus-derived lymphocytes (T cells)¹. The primary rejection of histo-incompatible grafts is a choice example of this cell-mediated type of immunity. Although bone marrow-derived antibody-producing cells (B cells) may function in secondary or hyperimmune responses, the development of specific effector mechanisms is predominantly thymus dependent². The proliferative responses to lymphocyte-borne histocompatibility antigens in vitro also involve mainly thymus-dependent cells^3,4, although several studies with mixtures of allogeneic lymphocytes in culture (mixed lymphocyte reaction; MLR) have indicated that B cells are also capable of responding^3–9. The stimulus to proliferate can be a function of antigenic determinants carried by both T and B cells^5,10. One question that arises, then, is whether or not there exists a preferential interaction between T and B cells in allogeneic mixtures. The identity of the predominant cell types from normal peripheral lymphoid tissues that interact to give the proliferative allogeneic response has not been determined. Knowledge of the cell types that are involved in the MLR, may lead to a greater understanding of any immunological implications that this reaction may present.