MRC1 and renal fibrosis: To better define whether M2 macrophages represent the main source of TGF-β during renal fibrosis, we used a FACS aria analysis to sort M1 (F4/80+CD206-) and M2 (F4/80+CD206+) macrophages from kidneys, and compared their TGF-β mRNA expression using real time RT-PCR.