In vitro macrophage chemotactic generation from serum immunoglobulin G by neutrophil neutral seryl protease

A neutral protease with a molecular weight of about 14,00 was separated at acid pH from rabbit neutrophils and then partially purified by elution on DEAE-Sephadex, CM-Sephadex and Sephadex G-75 in that order. This enzyme was inactivated by diisopropyl fluorophosphate (DFP), phenylmethyl sulphonylfluoride (PMSF), soybean trypsin inhibitor (SBTI), or elastatinal, suggesting a seryl protease resembling elastase, but it failed to digest elastin-orcein. The enzyme seemed different from histonase of rabbit neutrophils because of its haemoglobin (3HHb)-degrading ability and of inactivation by heparin. The protease generated in vitro macrophage chemotactic activity from guineapig serum IgG. This chemotactic factor had a molecular weight similar to that of IgG and its chemotacic generation was accompanied by release of dialysable peptide(s). No generation of macrophage chemotactic activity from IgG was induced in vitro by elastase from pig pancreas or by neutral thiol protease from rabbit neutrophils.