can be also regulated by transmembrane molecules. For example, CD200-CD200R interaction inhibits macrophage/microglia func- tion [40,41]. Blocking CD200-CD200R interaction and stimula- tion of macrophage/microglia activation may enhance clearance of CNS myelin debris [36]. Given the crucial roles of CR3 in inflammation and the finding that myelin can initiate inflamma- tory responses in CR3-dependent manner, blocking CR3-myelin interaction may be beneficial for treatment of CNS injury. It has been shown that myelin clearance is mediated primarily by CR3, however, our in vitro and in vivo data showed that microglia cells expressing high level of CR3 have poorer efficiency for myelin clearance and myelin clearance by macrophages from CR3 KO mice was not impaired (see Supporting Information Figure S1 and S2), which consistent with the studies from other group showing myelin is not phagocytosed by microglia after SCI [42] and myelin phagocytosis by macrophages may be via galectin-3/Mac-2 [43]. These studies suggested that targeting CR3 may be possible to suppress myelin-induced inflammation without affecting myelin clearance. Supporting Information Table S1 Primer sequences for qRT-PCR Found at: doi:10.1371/journal.pone.0009380.s001 (0.04 DOC) MB References 1. Donnelly DJ, Popovich PG (2008) Inflammation and its role in neuroprotection, axonal regeneration and functional recovery after spinal cord injury. Exp Neurol 209: 378–388. 2. 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(A) Bone marrow-derived macrophages from WT and CR3 KO mice were incubated with myelin for 48 hours and cells were stained with Oil Red O and MBP antibody, respectively. (B) In vivo study showed that myelin debris can be phagocytosed by macrophage from WT and CR3 KO mice after spinal cord injury. Representative micrographs of myelin uptake by macro- phage in the injured spinal cord at 2 weeks after injury in WT and CR3 KO mice using confocal microscopy. Macrophage was labeled with IBA-1 (green) and myelin debris was stained by Oil Red O (red). Scale bar = 10 mm. Found at: doi:10.1371/journal.pone.0009380.s002 (3.94 MB TIF) Figure S2 Comparison of myelin uptake by bone marrow- derived macrophages and primary microglia cells. Bone marrow- derived macrophages and primary microglia cells were incubated with myelin for 3 hours. Non-ingested myelin was washed away with PBS and cells were lysed. Intracellular MBP was assessed by ELISA. Data were expressed as mean 6 SEM. 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