Published online before print August 1, 2006
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Physiology Program, Harvard School of Public Health, Boston, Massachusetts
1 Correspondence: Physiology Program, Harvard School of Public Health, 665 Huntington Avenue, SPH-2, Room 221, Boston, MA 02115. E-mail: lkobzik{at}hsph.harvard.edu
The macrophage Class A scavenger receptor MARCO (macrophage receptor with a collagenous structure) functions as a pattern-recognition receptor for bacterial components, but its role in responses to CpG oligonucleotide sequences (CpG-ODN) in microbial DNA has not been characterized. Phosphorothioate (PS)-linked CpG-ODN stimulated IL-12 and NO production in wild-type but not in MARCO-deficient, thioglycollate-elicited peritoneal macrophages. MARCO and the related class A receptor SR-A belong to a redundant system of receptors for PS ODNs. The ability of MARCO to bind CpG-ODNs and conversely, to costimulate IL-12 and NO production upon specific ligation with immobilized mAb is consistent with MARCO being a signaling receptor for CpG-ODNs, costimulating TLR9-mediated NO and IL-12 production in macrophages. In contrast to MARCO, SR-A is likely to mediate negative regulation of macrophage responses to CpG-ODNs. In particular, increased affinity toward SR-A may contribute to decreased potency of oligo G-modified CpG-ODNs in stimulating IL-12 production. The results suggest that differential involvement of activating and inhibitory membrane receptors, such as SR-A and MARCO, may underlie profound differences observed in biological activities of different ODN sequences.
Key Words: oligonucleotides interleukin-12 nitric oxide
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