Pooled stimulating cells as a "standard stimulator" in mixed lymphocyte culture

Lymphocytes from normal unrelated donors were pooled and used as stimulating cells in mixed lymphocyte culture (MLC). Different pools, each consisting of cells from 20 or 30 different donors, stimulated approximately the same amount of 3H-thymidine incorporation by a given responder, and this "plateau level" of incorporation was different for different responders. Stimulation by pools of 20 cells was highly correlated with the general "responsiveness" of responding cells as measured by their mean response to a large panel of stimulating cells. Such pools may be useful as "standard stimulators" in quantitating MLC stimulation, and perhaps also in evaluating lymphocyte responsiveness of patients.