The influence of prophylactic immunosuppressive regimens on natural killer and lymphokine-activated killer cells in renal transplant recipients

We investigated natural-killer cells in 81 renal transplant recipients (RTR) in order to define what kind of in vivo prophylactic immunosuppression could be responsible of the impairment of these NK cells. Cell-surface phenotyping was performed by direct immunofluorescence with Leu7 (CD57), Leu11 (CD16), and Leu19 (CD56) antibodies, in one- and two-color stainings. Functional properties were analyzed with freshly isolated nonadherent mononuclear cells (NK activity) and after in vitro activation with r-IL-2 (LAK activity), in cytotoxicity assays using K562 and Daudi tumor lines as specific targets. A flow cytometry technique using carboxy-Fluorodiacetate was applied to monitor the cytotoxicity of NK cells. Our data emphasize the already known deficiency of NK cells: both NK subsets (CD16+ and/or CD56+) and NK activity were decreased in RTR. Moreover, we demonstrated that the in vitro IL-2-induced LAK cytotoxicity was also diminished in RTR. NK cells and functions were normal in RTR treated with cyclosporine only, decreased in RTR treated with both cyclosporine and azathioprine, and at the lowest level in RTR treated with azathioprine without cyclosporine. A multivariate statistical analysis found a negative linear regression between the doses of azathioprine and the number of functions of NK cells, confirming that azathioprine was responsible for the deficiency of NK cells in our RTR.