Protein A is a 40-60 kDa surface protein originally found in the cell wall of the bacteria Staphylococcus aureus (SPA). SPA binds proteins from many of mammalian species, most notably IgGs, and helps inhibit phagocytic engulfment and acts as an immunological disguise via this type of interaction, thus the bacteria will disrupts opsonization and phagocytosis. SPA is known to bind with Fc region of immunoglobulins preferentially through interaction with the VH3 variable region of the heavy cha