Phagocytosis in Subacute Bacterial Endocarditis

Abstract

Previous studies have indicated that immune 7G-opsonins constitute the main molecular class of antibody involved in phagocytosis and killing of infecting organisms in subacute bacterial endocarditis of man (1-3). High titers of 7G-opsonins were documented among patients infected with a wide variety of Gram-positive bacterial species, including Streptococcus viridans, Microaerophilic streptococcus, Staphylococcus aureus, Staphylococcus epidermidis, and Diplococcus tmeumoniae (1). Moreover, antiopsonic effect was consistently noted when isolated human 19S anti-7-globulin factors or rabbit antisera specific for "yG were added to phagocytic systems (2). In vitro competition between heat-labile serum factors and human anti-'y-globulin factors could be readily demonstrated. Since anti-'y-globulin factors as well as the complement component sequence show primary reactivity for structures present on the Fc portion of "yG, it seemed important to explore the role of the Fc region of "y-globulln in phagocytosis. An attempt was therefore made to examine the specific contribution of Fc structures in conferring specific opsonic activity to 7S q,-globulin molecules. The effects of enzymatic digestion, mild reduction with mercaptoethanol, or treatment of ~,G-opsonin with the oxidizing agent sodium metaperiodate were studied. It appeared that several procedures capable of degrading or altering sites on the Fc portion of 7S "y-globulin abolished opsonic activity. Materials and MethodsOpsonins.--In most instances, patients with active bacterial endocarditis furnished the specific immune opsonins. Because only certain strains of bacteria showed a high degree of reproducibility and consistency in the phagocytosis system, all of the experiments utilized *

Receptors for human γG Globulin on human neutrophils

“…It is possible that the Fc structures active in combination with the cell surface receptors were partially destroyed during the 24 hour papain digestion, or that these structures require the configuration conferred by the tertiary structure of the whole molecule for their full activity. Previous studies in our laboratory have indicated that these structures can be inactivated by acetylation, carbamylation, amidination (27), or mild reduction (28). The (30).…”

Proteins of the cystic fibrosis respiratory tract. Fragmented immunoglobulin G opsonic antibody causing defective opsonophagocytosis.

“…In part, this is explained by the presence of immunoglobulin receptors of the Fc.y class on the surface membranes of macrophages obtained from normal human volunteers (1 1). Moreover, it is known that papain-or pepsin-digested IgG lacks opsonic activity (12), and that free Fc fragments inhibit rosetting and erythrophagocytosis of erythrocytes coated with immunoglobulins of like IgG subclasses (13). Our work had suggested that a defect in the Fc portion of CF-derived antiPseudomonas IgG interfered with macrophage phagocyte function by preventing proper receptor attachment and subsequent internalization of opsonized bacteria.…”

In Vitro Antibody-Enzyme Conjugates with Specific Bactericidal Activity

“…Studies with human antibody (SBE patient infected with two strains of S. aureus) Previous work has demonstrated that the constant or intermittent bacteremia of SBE is often associated with the production of potent heat stable IgG opsonins (19)(20)(21)(22). For this reason an SBE patient (ELL) whose organisms and serum were available was selected for study.…”