Nonimmunologic Mechanisms Nonimmunologic mechanisms that protect against pneumonia include filtration of air as it passes through the nasopharynx, the glottal reflex, laryngeal closure, the cough reflex, clearance of organisms from the lower airways by ciliated cells, and ingestion by pulmonary macrophages and PMNs of small bacterial inocula that manage to reach alveolar spaces. Respiratory virus infection, chronic pulmonary disease, or heart failure compromises these mechanisms, predisposing to the development of pneumococcal pneumonia. Immunologic Mechanisms Innate Immunity Innate immune mechanisms participate in clearance of pneumococci from the nasopharynx as well as in phagocytosis by PMNs and macrophages via the microbial pattern recognition.
