Comparative studies of immunoglobulin opsonins in osteomyelitis and other established infections

Abstract

The opsonic activity of serum and isolated immunoglobulin fractions has been studied in twenty patients with osteomyelitis, using a quantitative assay which measures phagocytosis and killing of bacteria by human polymorphonuclear leukocytes. Opsonic functions as well as agglutinating and complement-fixing antibodies were compared with normal human sera as well as with a control group of eighteen patients with miscellaneous established severe infections. A surprising lack of heat stable γG opsonic activity, particularly for various species of Staphylococcus aureus, was documented among many patients with chronic active osteomyelitis. A similar apparent deficiency or low level of heat stable γG opsonin was also demonstrated among some of the controls with severe soft tissue infections. These weak opsonins showed a marked contrast to the potent heat stable γG opsonin activity previously documented in sub-acute bacterial endocarditis. Heat stable γG opsonin proved to be present in effective concentration in Gram-negative infections of bone and in the control group. Evidence was obtained for competitive blocking of phagocytic mechanisms by relatively weak immune γG opsonins allowed to react with bacteria prior to contact with more potent γG opsonins subsequently added to the test system. High titres of agglutinating anti-bacterial antibodies contrasted with relatively low levels of complement-fixing antibodies in many patients with chronic osteomyelitis. Opsonic activities of both 7S and 19S fractions of heat inactivated sera were studied in sera from osteomyelitis patients and control infections. When phagocytosis-promoting properties were not detectable in such fractions, opsonic capacity could be effectively restored by adding fresh serum devoid of anti-bacterial antibodies but possessing complement activity. Opsonic capacity of serum fractions then depended on the marked facilitative effect of heat labile factors. Activity ratios were derived of opsonic activity to actual amount of immunoglobulin present acting in concert with a constant amount of complement.