Determination of IL-2 and cytotoxicity of killer cells in MTT colorimetry.

The activity of interleukin 2 (IL-2) in culture supernatants of lymphokine-activated killer (LAK) cells and tumor infiltrating lymphocytes (TIL) as well as cytotoxicity of LAK cells on cultured leukemic cells were determined by MTT colorimetry. The results showed that higher activity of IL-2 in culture supernatant of LAK and TIL cells was found; it could be used to support the culture of IL-2 dependent cell lines. The significant cytotoxicity of LAK cells on leukemic cell lines could be found in vitro, and it was consistent with the ratio of effector cells to target cells. The number of living leukemic cells is consistently related with the concentration of formazan metabolite of MTT. It suggested that the numbers of living cells and cytotoxicity of LAK cells could be estimated by determination of formazan metabolite OD value.