The natural mediator for PMN emigration in inflammation. V. The site of structural change in the chemotactic generation of immunoglobulin G by inflammatory SH-dependent protease.

In earlier work, a chemotactic factor (leucoegresin) specific for neutrophilic polymorphonuclear (PMN) leucocytes had been isolated from the inflamed site of Arthus reactions or cutaneous burns. The substance shared common antigenic sites with IgG, and was produced from normal rabbit IgG and human IgG by a purified neutral SH-dependent protease from inflammatory tissue. A similar chemotactic factor was also produced by papain from papain-resistant IgG of rabbit, mouse and man. The production of chemotactic factor by an inflammatory SH-dependent protease was similarly confirmed with rabbit antibody IgG specific for bovine serum albumin. The molecular size of the chemotactic factor was approximately 140,000, suggesting a minor structural change of the IgG molecule; it was indistinguishable from the molecular size of leucoegresin. The chemotactic generation was accompanied by a release of dialysable peptides from the IgG molecule without any release of fragments like Fab or Fc. The activity of the chemotactic factor was abolished by prolonged digestion with the SH-dependent protease, which was accompanied by an increased release of dialysable peptides. The SH-dependent protease did not produce Fab and Fc fragments even on such prolonged digestion. The minor structural change of the IgG molecule during chemotactic generation by the enzyme seemed to occur exclusively at the Fc portion. The prolonged digestion of antibody IgG with the enzyme did not affect its antigen-binding capacity.