Pulmonary collectins in innate immunity of the lung.
Pulmonary collectins, hydrophilic surfactant proteins A and D (SP-A and SP-D), have been implicated in the regulation of pulmonary host defence and inflammation. SP-A and SP-D directly interact with a variety of microorganisms including bacteria and viruses, and attenuate the growth of Gram-negative bacteria, Histoplasma capsulatum and Mycoplasma pneumoniae. The collectins are thought to contribute to bacterial clearance. These lectins augment the phagocytosis of the bacteria by macrophages. SP-A serves as an opsonin and stimulates the uptake of bacteria and bacillus Calmette-Guérin through a C1q receptor- and an SP-R210-mediated processes. The collectin also stimulates FcR- and CR1-mediated phagocytosis by activating the macrophages. In addition, SP-A and SP-D directly interact with macrophages and enhance the phagocytosis of Streptococcus pneumoniae and Mycobacterium by increasing cell surface localization of the phagocytic receptors, scavenger receptor A and mannose receptor. The collectins also modulate pulmonary inflammation. SP-A and SP-D bind to cell surface receptors including Toll-like receptors, SIRPalpha and calreticulin/CD91, and attenuate or enhance inflammation in a microbial ligand-specific manner. In this article we review the immunomodulatory functions of SP-A and SP-D and their possible mechanisms in direct actions on microbes, macrophage phagocytosis and modulation of inflammation.
Kuroki
Yoshio
Y
Department of Biochemistry, Sapporo Medical University School of Medicine, Sapporo, Japan.kurokiy@sapmed.ac.jp
Takahashi
Motoko
M
Nishitani
Chiaki
C
D000818:Animals; D037222:Collectins / Q000276:immunology*; D006801:Humans; D007113:Immunity, Innate; D008168:Lung / Q000276:immunology* / Q000382:microbiology; D008264:Macrophages / Q000276:immunology / Q000382:microbiology; D010587:Phagocytosis; D011014:Pneumonia / Q000276:immunology* / Q000382:microbiology; D037662:Pulmonary Surfactant-Associated Protein A / Q000276:immunology; D037663:Pulmonary Surfactant-Associated Protein D / Q000276:immunology
D037222:Collectins; D037662:Pulmonary Surfactant-Associated Protein A; D037663:Pulmonary Surfactant-Associated Protein D