The scavenger receptor MARCO is required for lung defense against pneumococcal pneumonia and inhaled particles.
Alveolar macrophages (AMs) express the class A scavenger receptor macrophage receptor with collagenous structure (MARCO), but its role in vivo in lung defense against bacteria and environmental particles has not been studied. We used MARCO-deficient mice to directly test the in vivo role of AM MARCO in innate defense against pneumococcal infection and environmental particles. In a murine model of pneumococcal pneumonia, MARCO(-/-) mice displayed an impaired ability to clear bacteria from the lungs, increased pulmonary inflammation and cytokine release, and diminished survival. In vitro binding of Streptococcus pneumoniae and in vivo uptake of unopsonized particles by MARCO(-/-) AMs were dramatically impaired. MARCO(-/-) mice treated with the "inert" environmental particle TiO(2) showed enhanced inflammation and chemokine expression, indicating that MARCO-mediated clearance of inert particles by AMs prevents inflammatory responses otherwise initiated by other lung cells. Our findings point to an important role of MARCO in mounting an efficient and appropriately regulated innate immune response against inhaled particles and airborne pathogens.
Arredouani
Mohamed
M
Physiology Program, Harvard School of Public Health, 665 Huntington Ave., SPH-II, Rm. 221, Boston, MA 02115, USA.
Yang
Zhiping
Z
Ning
YaoYu
Y
Qin
Guozhong
G
Soininen
Raija
R
Tryggvason
Karl
K
Kobzik
Lester
L
D000818:Animals; D018893:Bronchoalveolar Lavage; D001992:Bronchoalveolar Lavage Fluid; D002470:Cell Survival; D016207:Cytokines / Q000378:metabolism; D004797:Enzyme-Linked Immunosorbent Assay; D005434:Flow Cytometry; D007113:Immunity, Innate; D007249:Inflammation; D008168:Lung / Q000166:cytology / Q000276:immunology* / Q000382:microbiology / Q000473:pathology; D008264:Macrophages / Q000473:pathology; D016676:Macrophages, Alveolar / Q000276:immunology* / Q000382:microbiology / Q000473:pathology; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D010587:Phagocytosis; D011018:Pneumonia, Pneumococcal / Q000276:immunology* / Q000382:microbiology; D011485:Protein Binding; D011971:Receptors, Immunologic / Q000378:metabolism*; D013296:Streptococcus pneumoniae / Q000378:metabolism; D013997:Time Factors; D014025:Titanium / Q000494:pharmacology
D016207:Cytokines; C092228:Marco protein, mouse; D011971:Receptors, Immunologic; C009495:titanium dioxide; D014025:Titanium