The presence of MMT may reflect disease activity and fibrotic progression in human kidney disease and it may also explain the notion that the density and heterogeneity of the macrophage infiltrate determine the fate of renal inflammation and fibrosis.23, 24 It is of note that infiltration of M2 macrophages positively correlates with the progression of renal fibrosis in human kidney diseases.25, 26 In this setting, the present study identified that the large majority of MMT cells in human kidney fibrosis express the M2 marker, CD206. This evidence concerns the gene MRC1 and renal fibrosis.