Studies on the inhibition of macrophage migration induced by soluble antigen-antibody complexes

Abstract

Mixtures of serum of Freund's complete adjuvant (FCA) immunized guinea-pigs and tuberculin PPD consistently inhibited the in vitro migration of peritoneal exudate cells (PEC) of normal guinea-pigs. It is shown that this inhibitory effect is due to a soluble complex between an IgG2 antibody and PPD. By separation of PPD on Sephadex G-200 two peaks were obtained, corresponding respectively to molecular weights of at least 800,000 and 25,000, separated by a plateau. Material derived from both peaks and from the plateau was able to form inhibitory complexes with anti-PPD IgG2. When a mixture of small molecular weight PPD and anti-PPD IgG2 was fractionated on Sephadex G-200, the inhibitory activity was recovered in the void region only. The detection of both IgG2 and PPD in the latter was taken as evidence for the presence of a high molecular weight antigen-antibody complex. When the mechanism of complex-induced inhibition of migration was examined it was found that: (1) complexes act directly on macrophages present in the peritoneal exudate; (2) removal of the Fc fragment of IgG2 by pepsin abolishes its ability to form migration inhibitory complexes; (3) passive sensitization of macrophages with anti-PPD IgG2, followed by exposure to PPD does not result in inhibition of migration; (4) in order to obtain migration inhibition, the complexes must be present during the entire migration period. A 2-hr pulse with complexes does not induce permanent inhibition; (5) the migration inhibitory activity of antigen--antibody complexes can be abolished by certain concentrations of puromycin and aminophylline.