Suppressive effect of IgA soluble immune complexes on neutrophil chemotaxis

The effect of IgA and IgG soluble immune complexes (SIC) on neutrophil chemotaxis was investigated. Six types of SIC were prepared from kappa-type IgA and IgG myeloma proteins: IgA-anti-kappa chain antibody SIC in IgA excess, IgA-anti-kappa chain antibody in SIC in anti-kappa chain antibody excess, IgA-anti-alpha chain antibody SIC in IgA excess, IgG-anti-kappa chain antibody SIC in IgG excess, IgG-anti-kappa chain antibody SIC in anti-kappa chain antibody excess, and IgG-anti-gamma chain antibody SIC in IgG excess. Three types of IgA SIC had a marked suppressive effect on neutrophil chemotaxis, while IgG SIC, free IgA, free anti-kappa chain antibody, and free anti-gamma chain antibody showed no inhibitory activity. This suppressive effect on neutrophil chemotaxis caused specifically by polymerized IgA was a cell-directed one and was expressed in a concentration dependent manner.