Opsonization of serum-sensitive and serum-resistant Escherichia coli by rough mutant (Re) antisera

The antibody binding and susceptibility to opsonization of 11 SR and five SS Escherichia coli strains by pooled high-titered rabbit antisera against the core-defective Re chemotype mutant of Salmonella minnesota R595 were studied. Binding of antibody was assessed by an IFA method, and the phagocytic rate was quantitated by measurement of the oxygen consumption of PMNs during phagocytosis. A significant correlation was demonstrated between the property of serum sensitivity and both antibody binding (p less than 0.001) and enhanced susceptibility to phagocytosis (p less than 0.01) after opsonization of these E. coli with rough mutant antisera. Opsonic activity was heat-stable and was primarily in the serum igG fraction. Opsonic antibody was reduced markedly by absorption with the methanol-fixed Re mutant but was only partially reduced by absorption with solvent-extracted Re CGL. IgG antibodies capable of mediating phagocytosis and directed against both extractable and nonextractable antigens of the core-defective Re mutant of S. minnesota R595 reacted with strains of E. coli isolated from neutropenic patients.