Suppression of leucocyte chemokinesis and chemotaxis by human IgA

The effects of IgA and IgG isolated from normal human serum on neutrophil and monocyte migration were examined. IgA inhibited neutrophil chemotaxis towards casein and neutrophil random migration in serum-containing medium. The dose-response curve for the inhibition of the two forms of stimulated cell movement was similar suggesting that inhibition of both forms of movement may occur by a common mechanism. It was concluded that the inhibition was mediated by polymeric and aggregated forms of IgA but not by IgA present in normal serum. IgA at concentrations which inhibited stimulated cell movement did not inhibit the phagocytosis of zymosan particles by neutrophils. In contrast to IgA, aggregated IgG did not inhibit neutrophil chemotaxis at concentrations which were markedly inhibitory to random migration in serum-containing medium, indicating a differential effect of IgA and IgG aggregates on cell migration.