Stimulating cell types in the autologous mixed leukocyte reaction in man.

Abstract

Abstract Although there is general agreement that the responding cell type in the autologous mixed leukocyte reaction (MLR) is a T cell, the identity of the stimulating cell type is controversial. We used a series of G-10, anti-human F(ab′)2-G-200, and E rosette techniques to separate mononuclear (MN)3 cells from 16 healthy donors into enriched populations of T cells, B cells, monocytes, and null cells. All cell types were used as responders against each cell type as stimulator (after 4000 R). T cells were superior to all other populations as responders to autologous stimulators. In comparative studies using different stimulator cell types with T cells as responders, monocytes produced the highest (stimulation index (SI) 78.7), null cells an intermediate (SI 20.1), and B and T cells a negligible (SI 2.6 and 1.0 respectively) level of stimulation. Although monocyte-depleted MN cells failed to stimulate autologous lymphocytes, the addition of increasing numbers of monocytes resulted in a steady rise in stimulation until high cell densities were reached. Monocyte-depleted non-T cells (B plus null cells) were also capable of stimulating autologous T cells. Reducing the number of B cells in the monocyte enriched population to <3% resulted in enhanced T cell stimulation. These experiments confirm that T cells are the principle responding cell type in the autologous MLR and indicate that the best stimulators in decreasing capacity are monocytes and null cells with essentially no stimulation produced by B cells or T cells.