Donor-specific blood transfusion prolongs survival of fully allogeneic ACI (RT1a) renal grafts in PVG (RT1a) recipients from 6-8 days to greater than 100 days. To determine how DSBT alters effector cytotoxic cell responses, we tested freshly isolated peripheral blood lymphocytes, spleen cells, and graft infiltrating cells (GIC) from pairs of PVG recipients of ACI kidneys pretreated with DSBT or autologous blood transfusion (ABT) for cell-mediated lympholysis, antibody-dependent cellular cytotoxicity (ADCC), and natural killer activity at the day of transplantation (day 0) and days 3 and 6 posttransplantation. PBL and GIC from the same pairs of animals were examined for their phenotypic profile (CD4, CD8, 3.2.3 NK cell marker, IL-2 receptor). CML, ADCC, and NK activity were higher in PBL than splenocytes of GIC of both ABT and DSBT groups at all time points examined. CML activity of PBL at day 3 was significantly higher in DSBT vs. ABT recipients (P less than 0.01), while at day 6 both groups were equally elevated. Splenocytes demonstrated significantly lower CML activity in DSBT vs. ABT recipients at day 6 (P less than 0.05). CML activity of GIC eluted from ABT and DSBT kidneys was not detected at day 3, but was significantly elevated and equivalent in both groups at day 6. ADCC and NK activities of PBL did not differ between ABT and DSBT groups, and were negligible in splenocytes. GIC demonstrated higher NK activity in DSBT vs. ABT recipients at day 3 (P less than 0.05), while ADCC activity was not detectable at any time in either group. Phenotypic analysis of PBL and GIC at day 3 showed no significant differences between ABT and DSBT groups in the percentage of CD4 or CD8 cells. However, in both ABT and DSBT groups the ratio of CD4:CD8 cells was markedly lower in GIC than PBL. By day 6, PBL from both ABT and DSBT groups showed equivalent and significant decreases in CD4+ cells and increases in CD8+ and 3.2.3+ (NK) cells. The percentage of IL-2R+ cells remained low (less than 5%) in both groups at day 3. In contrast, at day 6 there was a significant increase in IL-2R+ (and to a lesser extent CD4+) GIC in ABT- but not DSBT-treated recipients, while CD8+ cells were significantly increased in both groups.(ABSTRACT TRUNCATED AT 400 WORDS)