the influence of perforin expression on the sensitivity of lak/nk killing against various tumor target cells

background: perforin is known to be important in cytolytic activity mediated by natural killer (nk) cells.   objective: to study the relationship between the efficiency of nk and lymphokine-activated killer (lak) cells activity, and the expression of perforin and hla class i molecules.   methods: lak cells were generated by in vitro culturing of human peripheral blood lymphocytes (pbls) in the presence of human recombinant interleukin-2 (ril-2). cytotoxic activity was measured at different intervals of activation by mtt colorimetric assay using different human tumor cell lines. immunocytochemical staining of molecules was performed on lak/nk cells using specific monoclonal antibodies and biotin-conjugated anti-immunoglobulin. results: lak/nk killing against fen and two other cell lines, kb and scaber showed that at day 9 and 15 of activation, 57% to 60% and 45.5% to 92.5% of fen cells were killed at different e/t ratios. at the same time, the maximum percent killing against scaber and kb cell lines was 47.3 and 54.3 at 5/1 ratio, respectively, showing that fen cells were more sensitive than the two other cells. time-course experiments using fen cell line demonstrated 60.0, 83.9 and 34.8 percent killing at days 9, 15 and 22 at 10/1 e/t ratios. when other e/t ratios were investigated, a similar profile was observed. the maximum activity was at day 15 and 5/1 e/t ratio (92.5%). in immunocytochemical staining of activated lak cells, 75.9% to 86.3% of lak cells expressed hla class i molecules. perforin expression changed from 30.3% at day 7 to 42.7% at day 17 followed by a decrease to 27.9% at day 24.   conclusion: these data indicate that perforin expression is closely correlated with nk/lak killing activity.