Immunoregulation of lymphokine-activated killer cells

The in vitro effects of Concanavalin A (Con A) and prednisolone (PRD) on the cytotoxic functions of lymphocytes and the generation of lymphokine-activated killer (LAK) cells were investigated. Con A at concentrations ranging from 1 to 40 micrograms/ml did not significantly affect the cytotoxicity of LAK cells when added directly to the effector and target cell mixture in a 4-hr 51Cr release assay. The generation and lytic capacity of LAK cells were significantly affected by Con A in a dose-dependent manner when lectin was added at the initiation of culture. Suppression of LAK cell activity was demonstrable at effector: target (E:T) cell ratios. Lymphocyte cultures incubated with PRD at concentrations ranging from 10(-9) to 10(-4) M showed a decrease in both the numbers of and activity of LAK cells using a variety of target cells. Pretreatment of target cells with either PRD or Con A did not affect their sensitivity to lysis by LAK cells and incubation of lymphocytes with Con A did not induce autoreactive cytotoxic or suppressor cells directed against LAK cell activity. Thus while PRD and Con A can inhibit the generation of LAK cells, they also directly inhibit their specific cytotoxic activity on a per cell basis. These results suggest that like other cytotoxic cells, LAK cells are also under active immunologic control.