METHODS. Bone marrow macrophages were stimulated with IL-4 for 48hr to induce alternative activation. In vitro, the polarisation of WT, CCR2-KO, and CX3CR1-KO macrophages were compared phenotypically (PCR, flow cytometry) and functionally (arginase activity, nitric oxide production, cytokine secretion). In vivo, the ability of WT and KO AAMs were tested in their ability to block DNBS colitis. Cells were administered ip to WT mice 2d prior to the induction of colitis; mice were necropsied 3d later.
RESULTS. The lack of CCR2 or CX3CR1 did not impair the ability of macrophage to alternatively activate as observed by AAM mRNA expression of Arg1, Ym1, Retnla. AAMs were also similar in their functional parameters. In mice, both WT and KO transferred AAMs afforded protection against DNBS colitis as demonstrated by reduced colon shortening and reduced macroscopic/microscopic damage scores.
DISCUSSION. These data show that ip-transferred AAMs protect against DNBS colitis and do not require the expression of CCR2 or CX3CR1 to do so. As a treatment for inflammatory bowel disease, the results suggest that AAMs may be an effective therapy even in the absence of these chemokine receptors.