IL2 and renal fibrosis: Accordingly, at initial stages of collagen deposition and renal fibrosis, type III collagen appears in greater amounts than do type I. As renal fibrosis progresses, there is a proportional decrease in type III collagen, and tubulointerstitial fibroblasts secrete collagen types I, III, IV, and V in response to TGF-beta, epidermal growth factor, and interleukin-2 [53, 54].