Relative neutralizing activity in polyspecific IgM, IgA, and IgG preparations against group A streptococcal superantigens

In this study we compared the ability of different immunoglobulin Og) prepa rations containing IgG, IgM, and/or IgA to neutralize the activity of strep tococcal pyrogenic exotoxin A (SpeA) or culture supernatant from a clinical group A streptococcal isolate. All Ig preparations markedly inhibited the mitogenic and cytokine-inducing activity of SpeA and culture supernatant at concentrations of 0.05-0.5 mg/mL, and at 0.5 mg/mL, most caused 95-100% in hibition of both stimuli. A significantly higher (P less than or equal to . 05) inhibition of SpeA was achieved by Pentaglobin (IgG, IgM, and IgA) and IgAbulin (IgA and IgG), as compared with pure IgG preparations. IgM- and Ig A-enriched preparations had significantly higher inhibitory activity agains t SpeA than against culture supernatant, whereas the reverse was true for t he IgG preparations (P less than or equal to .05), The data show that IgM a nd IgA are potent inhibitors of specific streptococcal superantigens, These findings may have implications for the optimization of immunotherapy in in vasive streptococcal infections.