Diagram of the main pathways and components of the human complement system 3a and a schematic representation of S. aureus evading opsonization and phagocytic uptake by neutrophil 3b. Red boxes indicate staphylococcal proteins, and blue boxes indicate host proteins. Abbreviations: IgG, immunoglobulin G; SpA, staphylococcal protein A; Sbi, staphylococcal binding of IgG; SCIN, staphylococcal complement inhibitor; SAK, staphylokinase; Aur, aureolysin; SSL, staphylococcal superantigen-like protein; Efb, extracellular fibrinogen-binding protein; Ecb, extracellular complement-binding protein. The figure was adapted from Servier Medical Art.