Suppression of the MLR by unfractionated or fractionated cells from day 4 leukapheresis samples. In (A) and (B), responder cells were cryopreserved PBL from the leukapheresis donor obtained before administration of G-CSF. Open bars show the mean ³H-TdR incorporation of triplicate wells with allogeneic stimulator cells, and closed bars show the incorporation with autologous stimulator cells. In (C) and (D), responder cells were fresh PBL from an unrelated normal individual. N, no cocultured cells added to the MLR; PBL, irradiated responder cells added to the MLR; U and C1-C5, unfractionated or fractionated irradiated day 4 leukapheresis cells added to the MLR. Standard errors were less than 10% of the mean values shown.