Figure 4 PD-1 promotes collagen-1 production in myofibroblasts. (A) The proliferation rate in co-cultured cells was lower than that in CD4+ T cells, but there was no significant difference compared with myofibroblasts. The S phase of CD4+ T cells, myofibroblasts, and co-cultured cells were 8.99, 19.12, and 21.49, respectively. (B) The content of collagen-1 in the co-culture system was higher than that in the single-culture system. (C) The addition of PD-1 blocker in the co-culture system can reduce the content of collagen-1. GAPDH protein was used as negative standard.