Human Immunity to Pseudomonas aeruginosa. II. Relationship between Heat-Stable Opsonins and Type-Specific Lipopolysaccharides

Abstract

The relationship between heat-stable opsomzing antibody in human serum and purified lipopolysaccharides (LPS) prepared from strains of Pseudomonas aeruginosa described in a serologic typing system by Fisher, Devlin, and Gnabasik was assessed by quantitative tests of phagocytosis and killing by polymorphonuclear leukocytes. Serum from human volunteers given purified LPS showed significantly increased opsonizing activity paralleled by rises in titers of antibody. These opsonins were type-specific, and purified LPS could block phagocytosis of the parent strain from which each was derived. The opsonizing activity in serum could be removed by absorptions with whole live bacteria, heat-killed intact bacteria, or LPS. These absorptions showed that there was no significant crossantigenicity in the typing system of Fisher, Devlin, and Gnabasik, but wild-type strains of P. aeruginosa commonly contained multiple LPS antigens. Heat-stable, somatic antigens of P. aeruginosa have properties enabling the organisms to resist phagocytosis; this resistance is neutralized by serum containing specific antibodies.