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The macrophage scavenger receptor SR-AI/II and lung defense against pneumococci and particles.

Arredouani MS, Yang Z, Imrich A, Ning Y, Qin G, Kobzik L

Physiology Program, 665 Huntington Avenue, SPH-II, Room 221, Boston, MA 02115, USA.

The class A macrophage scavenger receptor SR-AI/II is implicated as a pattern recognition receptor for innate immunity, but its functional role in lung defense has not been studied. We used mice genetically deficient in SR-AI/II and their wild-type C57BL/6 counterparts to investigate the contribution of this receptor to defense against pneumococcal infection and inhaled particles. SR-AI/II deficiency caused impaired phagocytosis of fluorescent bacteria in vivo, diminished clearance of live bacteria from the lungs, and substantially increased pneumonic inflammation. Survival studies also showed increased mortality in SR-AI/II-deficient mice with pneumococcal lung infection. Similarly, after challenge of the airways with TiO(2) particles, SR-AI/II-deficient mice showed increased proinflammatory cytokine levels in lung lavage fluid and a more pronounced neutrophilic inflammation. The data indicate that the lung macrophage class A scavenger receptor SR-AI/II contributes to innate defense against bacteria and inhaled particles.

Published 18 September 2006 in Am J Respir Cell Mol Biol, 35(4): 474-8.
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