Antibacterial activity of the contact and complement systems is blocked by SIC, a protein secreted by Streptococcus pyogenes.
Recent studies have shown that activation of the complement and contact systems results in the generation of antibacterial peptides. Streptococcus pyogenes, a major bacterial pathogen in humans, exists in more than one hundred different serotypes due to sequence variation in the surface-associated M protein. Cases of invasive and life-threatening S. pyogenes infections are commonly associated with