In experimental peritonitis, SOCS3 mRNA silencing in macrophages caused elevated expression of the M2 phenotypic markers Il10, Mrc1, and Arg164, which is consistent with the inverse relationship we observed between elevated Socs3 expression in CD11b/LIF BMT recipients and reduced expression of Il10, Arg2, and Mrc1. Together, these observations suggest that the shift of CD11b/LIF macrophages away from an M2-biased phenotype in mdx BMT recipients may result, in part, from LIF induction of Socs3 after the transgenic macrophages enter the diseased muscle. The gene discussed is ARG2; the disease is peritonitis.