Specificity of opsonic antibodies to enhance phagocytosis of Pseudomonas aeiuginosa by human alveolar macrophages

specific secretory IgA (sIgA) and IgG antibodies to promote phagocytosis of viable Pseudomonas aeruginosa by human alveolar macrophages. Macrophages were obtained by lung lavage of normal adult smoker and nonsmoker volunteers and were maintained as in vitro cell monolayers. Both immune sIgA and IgG agglu-tinating antibodies were demonstrated to coat and op-sonize viable bacteria, whereas similar nonimmune im-munoglobulin preparations did not. When alveolar mac-rophages were challenged with viable opsonized '4C-la-beled Pseudomonas, IgG-reacted bacteria were ingested better and killed more readily than sIgA-opsonized organisms. Phagocytic responses were not significantly different between macrophages obtained from smokers and nonsmokers. Although sIgA and IgG antibodies can be found in respiratory secretions and both are un-doubtedly important in pulmonary host defense, IgG opsonic antibody was superior in enhancing the uptake of Pseudomonas by in vitro-cultured alveolar macro-phages. It may be the more important respiratory antibody for certain bacterial infections