METALLOPROTEASE AND SERINE-PROTEASE ARE INVOLVED IN CLEAVAGE OF CD43,CD44, AND CD16 FROM STIMULATED HUMAN GRANULOCYTES - INDUCTION OF CLEAVAGE OF L-SELECTIN VIA CD16

CD43, CD44, CD16, and L-selectin have been previously shown to be enzy matically cleaved from stimulated leukocytes. However, little is known about the enzymes involved in these processes. Here, metalloprotease( s) inhibitable by 1,10-phenanthroline together with serine protease(s) inhibitable by Nalpha-p-tosyl-L-lysine chloromethyl ketone and 3,4-di chloroisocoumarin are shown to be involved in the cleavage of CD43, CD 44, and CD16 but not in the cleavage of L-selectin on granulocytes. in addition, mAbs that recognize these individual receptors and induce t heir specific cleavage did not initiate cleavage of the others. In one case only, L-selectin, cleavage was also triggered by mAbs interactin g with CD16 (the low affinity FcgammaR). Thus, this mechanism represen ts a novel pathway of L-selectin cleavage induction.