Surfactant protein (SP)-A and SP-D, immunoglobulins, and complement all modulate
inflammation within the lung by regulating pathogen clearance. For example, SP-A binds to
and opsonizes a variety of bacteria and viruses, thereby enhancing their phagocytosis by
innate immune cells such as alveolar macrophages. Immunoglobulins, which bind to
antigen and facilitate Fc receptor-mediated phagocytosis, can also activate complement, a
family of soluble proteins with multiple host defense functions. Previous studies showed that …