COMPARISON OF THE EFFECTS OF PURIFIED HUMAN ALPHA-1-ANTICHYMOTRYPSIN AND ALPHA-1-PROTEINASE INHIBITOR ON NK CYTOTOXICITY - ONLY ALPHA-1-PROTEINASE INHIBITOR INHIBITS NATURAL KILLING

While an inhibitory effect on natural killer (NK) cell activity was demonstrated with partially purified α1Achy, neither highly purified α1Achy from two healthy donors nor from one patient with giant-cell arteritis, which carries more highly branched glycans, inhibited the NK. cytotoxicity. Our purification procedure, based on immunoaffinity chromatography and gel filtration, was not in question since the pure α1-proteinase inhibitor (α1PI) prepared in our laboratory by using a similar procedure continued to inhibit the NK cytotoxicity. If an inhibitory effect not related to antiprotease activity occurs with α1PI, it is surprising that it is not shared by α1Achy which, like α1PI, belongs to the serpin family and which possesses a strong structural homology with α1PI. Our finding that α1PI is able to affect human NK cytotoxicity while α1Achy (even with more highly branched glycans) is unable to suggests that events controlling NK activity may involve other enzymes than chymotrypsin-like enzymes. © 1990.