Elevated natural killer (NK) cytotoxicity of mononuclear leucocytes from splenectomized patients: increase in Leu-7+ and Leu-11+ leucocytes.

The natural killer (NK) cell cytotoxic activity (against K562 targets) of peripheral blood mononuclear leucocytes (MNL) from patients splenectomized for trauma was examined. The data were fitted to a mathematical model from which the values for maximal cytotoxicity, and the number of MNL required to achieve 25% cytotoxicity (LD25-, were computed. The results showed that the NK cell cytotoxicity of MNL from splenectomized patients was significantly elevated at all effector/target cell ratios tested (1:1 to 100:1), compared to normal subjects. In the splenectomized group there was a significant increase in the maximal cytotoxicity and a significant reduction in the LD25. Flow cytofluorometry studies revealed an increase in percentage and absolute numbers of cells bearing Leu-7 or the Leu-11 antigens in MNL of splenectomized patients. We found that there was a significant correlation between the percentage of Leu-11+ cells and the NK cytotoxicity (both maximal and LD25) but not between Leu-7+ and these parameters, for both the controls and splenectomized subjects. This suggests that the increased NK cytotoxicity by the MNL of splenectomized patients may be due wholly or partly to an increase in the proportion of cells expressing the Leu-11+ antigens.