EXPRESSION AND FUNCTIONAL-ROLE OF DIPEPTIDYL PEPTIDASE-IV (CD26) ON HUMAN NATURAL-KILLER-CELLS

The expression and functional role of dipeptidyl peptidase IV (DP IV, CD26, EC 3.4.14.5) was studied on human natural killer (NK) cells. Her e we show that freshly isolated NK cells do express only low amounts o f DP IV. However, after IL-2 stimulation of NK cells (70% purity) surf ace DP IV expression was significantly increased in a subpopulation (3 0%) of these cells. Specific DP IV inhibitors (Lys-[Z-(NO2)]-piperidid e, Lys-[Z-(NO2)]-thiazolidide) and polyclonal antibodies directed agai nst the ectopeptidase suppressed DNA synthesis and cell cycle progress ion of NK cells. The natural cytotoxic activity of DP IV+ CD56+ cells was found unchanged in comparison to those of DP IV- CD56+ cells. DP I V inhibitors had no effect on the natural cytotoxicity of mononuclear cells. From these data we conclude that DP IV is involved in the regul ation of proliferation of NK cells, whereas natural cytotoxicity seems to be regulated independently.