HEAT LABILE OPSONINS TO PNEUMOCOCCUS

Abstract

Heat labile opsonins (HLO) in normal rat serum to both encapsulated and unencapsulated pneumococci (a) have the same heat lability as complement (C); (b) are active at 37°C but not at 0°C; (c) are inactivated proportionately to hemolytic C by the addition of immune aggregates to the serum; (d) are adsorbed from serum nonspecifically by bacteria at 37°C but not at 0°C; (e) are Ca⁺⁺- and/or Mg⁺⁺-dependent in their action; and (f) are inactivated by zymosan and a purified cobra venom factor, and in the case of encapsulated pneumococci, at least, by NH₄OH. Like other opsonins, HLO to pneumococci act primarily on the bacteria rather than on the phagocytes. Their combined properties indicate that they involve multiple components of the hemolytic C system.