Autologous mixed lymphocyte reaction in man: further characterization of responding cells

Experiments were performed to determine the type of cells undergoing thymidine incorporation in 7-day autologous mixed lymphocyte reactions (AMLR). Peripheral blood mononuclear cells (PBM) were separated into B cells, T cells, B + Null cells and T + Null cell-enriched populations. Cells were cultured in various combinations. Monocytes were removed to determine their influence on AMLR. The main thymidine-incorporating cells in cultures were shown to be Null cells and to a lesser extent T cells. Monocytes were found to have a more pronounced suppressor effect on stimulation of T cells by non-T cell populations in younger individuals than in the elderly. Whether Null cells undergo a spontaneous blastogenesis in culture or are stimulated by T or B cells, could not be answered by the present investigation.