Plays a role in the inhibition of host complement-mediated lysis and serum bactericidal activity by interacting with complement component C5 (PubMed:23797068). Affects all three pathways of complement activation and inhibits the cleavage of C5 by preventing its binding to C5 convertases. In turn, prevents C5a-mediated neutrophil migration (By similarity). Interacts with host IgA and complement C5. Belongs to the staphylococcal/streptococcal toxin family.