NOVEL MONOCLONAL-ANTIBODIES AGAINST MEMBRANE STRUCTURES THAT ARE PREFERENTIALLY EXPRESSED ON IL-2-ACTIVATED RAT NK CELLS

Interleukin-2 (IL-2)-activated natural killer (NK) cells are known to mediate specific functions such as cytolytic activity and tumor infilt ration more efficiently than nonactivated NK cells. To investigate whe ther these characteristics are associated with induction or up-regulat ion of expression of membrane structures after IL-2 activation, we sel ected four hybridomas (mAbs ANK44, ANK66, ANK7, and ANK123) derived fr om mice immunized with rat IL-2-activated NK cells and compared the ex pression of the epitopes recognized on IL-2-activated NK cells versus unstimulated NK cells. We found that ANK44-expression was induced afte r activation with IL-2, The antigens recognized by ANK66, ANK7, and AN K123 were expressed selectively on subsets of nonactivated NK cells. A fter activation with IL-2 the level of expression of these antigens wa s increased. Moreover, the majority of NK cells then expressed these a ntigens after IL-2 activation. Biochemical characterization of the mem brane structures recognized on IL-2-activated NK cells showed that the y have not previously been described. The precise function of these me mbrane structures is not yet known, however, the selective nature of t heir expression implies their involvement in the specific functions of IL-2-activated NK cells.