Opsonic Activity of Agammaglobulinemic Human Sera

Two sera from adult patients with agammaglobulinemia were studied for their opsonic capacity—e.g., their ability to enhance phagocytosis and killing of several test bacterial species. The sera contained normal amounts of hemolytically active complement but no more than trace amounts of immunoglobulins. Distinct heat labile opsonic activity was demonstrable for several bacterial strains including Staphylococcus aureus, Streptococcus epidermidis, Streptococcus viridans, Streptococcus faecalis, and Serratia marcescens. Opsonic activity was abolished by heat inactivation at 56°C or by absorption of sera with rabbit antigen-antibody precipitates. These findings indicate that heat labile factors may play a primary role in some human phagocytic systems.