LACK OF EVIDENCE FOR NATURAL CYTOTOXICITY DEFICIENCY AGAINST HUMAN EX-VIVO TUMOR-CELLS IN ALLOGRAFT RECIPIENTS

Background. Allograft recipients, who have a high risk of developing m alignancies, are deficient in natural killer cells which mediate natur al cytotoxicity against tumour cells. We evaluated the relevance of NK deficiency in transplant patients with regard to the natural lysis of human tumour cells. Methods. Target cells were ex vivo tumour cells, obtained from solid tumours from kidney transplant patients and non-im munocompromised patients. Peripheral blood was extracted from kidney r ecipients and from normal controls. mononuclear cells were separated a fter anti-CD3 and anti-TCR immunostaining to obtain NK and T cell subs ets. LAK cells were obtained by in vitro IL2-activation. For each tumo ur, natural cytotoxicity assays were performed to compare effector cel ls from a kidney recipient with those from a normal control. Twenty-se ven solid rumours, either allogenic or syngenic, were analysed, mainly consisting of renal, colon, and skin carcinomas. Results. Natural cyt otoxicity assays on K562 targets confirmed the expected NK deficiency in the kidney recipients. However, the NK and LAK cells from the kidne y recipients did not kill a smaller number of tumour target cells than the controls, whatever the tumour type, under both the syngenic and a llogenic conditions. Conclusions. We conclude that natural cytotoxicit y against human tumour cells cannot be extrapolated from the cytotoxic ity assays with established cell lines, and that natural lysis of ex v ivo human tumour cells is not impaired in transplant patients.