Natural killer cell subsets in long-term renal allograft recipients. A phenotypic and functional study

Natural Killer cell subsets were studied in 39 long-term renal allotransplant recipients receiving conventional immunosuppression and 26 normal controls. Two-color flow cytometry analysis was used to determine coexpression of 2 surface antigens known to allow a phenotypic and functional discrimination of NK cells--Leu-7 a marker of large granular lymphocytes, and Leu-11c directed against the FcgammaR. In 11 patients and controls, these NK cell subsets were compared with actual NK activity assessed by killing of K562 target cells. Our data clearly show that, in long-term kidney recipients, the absolute number of NK cells (Leu-11c+) is significantly decreased compared with that of the control group. Furthermore, the most cytotoxic NK cell subset (Leu-7-/Leu-11c+ phenotype) is markedly diminished in the transplant population, whereas the less cytotoxic subset (Leu-7+/Leu-11c+) is unchanged. Finally, actual NK cell activity closely correlates with both relative and absolute numbers of these 2 NK cell subsets. These data provide convincing evidence that NK activity is impaired in long-term kidney recipients because of a diminished number of NK effector cells.