Prothymosin alpha enhances human natural killer cell cytotoxicity: role in mediating signals for NK activity.

We have investigated the effects of prothymosin alpha (ProT alpha) on the in vitro NK activity of various human cell populations obtained by successive purification of large granular lymphocytes (LGLs) and CD16+ cells. The results of this study indicate that ProT alpha is able to enhance the spontaneous NK activity of cells from normal donors. This effect was time and dose dependent in the range 7 to 350 nM, occurred over a wide range of effector/target cell ratios, and appeared not to require the presence of accessory cells. In addition, ProT alpha exhibited additive effects with recombinant interferon-gamma (rIFN-gamma) and recombinant interleukin-2 (rIL-2). Finally our data suggest that the effect of ProT alpha enhancing the NK cell cytotoxicity appears to involve enhancement of p70 IL-2R expression and internalization of IL-2, and was independent of cell proliferation.