Regulation of neutrophil functions by elastase-generated IgG fragments

IgG is split by neutrophil elastase into Fc and Fab fragments. These IgG fragments influence the functions of stimulated neutrophils such as chemotaxis, oxidative burst, and enzyme release. FMLP stimulated leukocyte chemotaxis is specifically inhibited by the elastase generated Fc fragments. Seven nmol Fc/10(6) PMN totally inhibit the chemotaxis stimulated by 16 to 125 nM FMLP. Native IgG and Fab fragments show no effect. FMLP-stimulated superoxide anion generation is specifically inhibited by Fc fragments with half maximal inhibition by 1.2 nmol/10(6) PMN. The generation of hydrogen peroxide is concomitantly stimulated, resulting in a superoxide dismutase-like effect. FMLP-stimulated elastase and myeloperoxidase release are enhanced by Fab fragments (10 nmol/10(6) PMN) to 206 and 155%, respectively, of reference values by 25 nM FMLP, while Fc and native IgG stimulate to a less extent. Consequently, elastase-generated Fc fragments have an inhibitory effect on inflammation by reducing chemotaxis and oxidative burst of stimulated neutrophils. The release stimulating activity of Fab fragments results in an up-regulation of elastase induced IgG degradation.