Interleukin-3 and interleukin-4 each strongly inhibit the induction and function of human LAK cells.

We have examined some of the factors which may regulate the generation and function of human lymphokine-activated killer (LAK) cells. In particular we have studied the effect of cytokines other than interleukin-2 on the ability of human LAK cells to kill human tumour cells. By exposing human tumour cells to human LAK-cells in the presence and absence of interleukin-3 or interleukin-4, we were able to demonstrate that each of these cytokines was able to severely reduce the amount of tumour cell killing. Additionally, we examined the effect of interleukin-3 or interleukin-4 on the production in vitro of human LAK cells by including these materials with interleukin-2 while LAK-cells were being induced. These results showed that not only were these cytokines able to inhibit human LAK-cell function, but they were also able to strongly reduce the ability of interleukin-2 to generate human LAK-cells.