The mixed lymphocyte reaction: selective activation and inactivation of the stimulating cells.

Allogeneic cells pretreated for 48 hr with 2 × 10^?6M ouabain have lost the capacity to show the mixed lymphocyte reaction (MLR). Analysis of various combinations of cells in the one-way MLR revealed that this effect was on the stimulating cells and not on the responding cells. Pretreatment of cells from both donors with 10^?7M ouabain caused no change in incorporation of labeled thymidine into DNA during the first 5 days of mixed lymphocyte culture; thereafter, as incorporation by the controls declined, that of the pretreated cells continued to increase. This effect was also on the stimulating cells and not on the responders. The irreversible effects of ouabain are thus either to activate or inactivate the stimulating cells depending on the concentration of the drug; there is little or no effect on the responding cells.