RETNLB and renal fibrosis: M2 macrophages, which highly express Arg1, CD206 and chitinase-like proteins such as Ym1 and Fizz1 provide for repairing the affected tissue, but upon chronic injury, they promote renal fibrosis through paracrine effects or direct transition to myofibroblast-like cells, via the process of macrophage-to-myofibroblast transition [64].