Release of lysosomal enzymes from human polymorphonuclear leukocytes by soluble intermediate immune complexes

The efficacy of soluble immune complexes (1C) of different sizes prepared in vitro or present in RA sera and synovial fluids to induce the release of beta-glucuronidase (BG) and neutral protease (NP) from PMN has been examined. Immune complexes of human HGG-rabbit anti-human HGG prepared in 5, 10 and 20 times excess of antigen equivalence were fractionated into three pools, PI (22S--13S), PII (13S--7S) and PIII (7S) using Sephadex G-200 column chromatography. NP and BG-releasing activity was mostly associated with PII. Similar fractions were obtained from RA sera and synovial fluids. BG-releasing activity was again predominantly associated with PII. PII fractions from normal sera and from 2 non-RA IC disease sera showed less BG-releasing activity than the RA PII fractions. Negligible NP release was observed with all three serum pools. Further investigation demonstrated the presence of NP inhibitor(s) in PI and PII from human sera.