A streptococcal erythrogenic toxin preparation augments natural killer activity of peripheral blood mononuclear cells

Natural killer (NK) activity in peripheral blood mononuclear cells is augmented by products released by two different strains of streptococci. This property is due at least in part to an erythrogenic toxin (ET). A preparation of physiologically active ET from strain NY5 group A beta-hemolytic streptococci and streptococcal products (SP) derived from the culture supernatants of ATCC strain 19165 group A streptococci were both potent inducers of NK activity. An anti-serum to ET reacted with two polypeptides in SP, one of which comigrated with ET when analyzed by SDS-PAGE. Using an affinity column with an antiserum to ET known to neutralize its mitogenic properties, the NK-enhancing activity of ET and SP was partly absorbed and was recovered upon elution. These findings suggest that immunologically related ETs in different streptococcal strains play a role in the activation of NK cells. This novel property of streptococci may feature in the pathogenesis of streptococcal infections and their protean manifestations.