Macrophage mediated tumor cytotoxicity--function of macrophages in human renal allograft recipients

It has been previously reported that human peripheral blood monocyte derived macrophages acquire enhanced cytotoxicity for tumor cells after incubation in either lymphocyte mediators or lipopolysaccharide. When the macrophages obtained from renal transplant recipients were studied we observed that the macrophages obtained from 1 to 4 year post-transplant survivors were cytotoxic for tumor cells whereas, macrophages obtained from renal transplant recipients at 10 days to 7 months post-transplantation have a depressed capacity to kill human tumor cells in vitro. Furthermore, in a long term study, eight renal patients were tested repeatedly up to 1 year post-transplant. All 5 renal transplant recipients showing no clinical evidence of rejection during this 1 year study were found to possess macrophages which were non-cytolytic for tumor cells whereas 2 of the 3 patients undergoing rejection crises did possess cytotoxic macrophages. Thus, it appears that at times of rejection crises, these patients' macrophages are converted into cytolytic cells.