Subpopulations of cells involved in the human mixed lymphocyte culture response.

Various subpopulations of human peripheral lymphoid cells were tested for their role in the mixed lymphocyte culture (MLC) response. Preparations of lymphocytes enriched for T cells, separated by a rosette sedimentation technique, were usually found to exhibit higher MLC responses than preparations enriched for B cells. The relatively high responses of B-cell-enriched preparations could largely be explained by contaminating T cells (approximately 5%) whose MLC reactivities were strongly enhanced by autologous non-T lymphocytes. Cell preparations enriched for B cells were found to be more potent stimulations of MLC responses than T-cell-enriched preparations in most responder-stimulator cell combinations. An MLC response could only be elicited in the presence of cells with characteristics of monocytes/macrophages. These cells could be derived from either the responder or the stimulator.