Although the receptor involved in PD-L1 signalling in vitro remains elusive in the latter study (fibroblasts were negative for PD-1), both studies suggest that the contribution of the PD-1/PD-L1 axis in pulmonary fibrosis is independent of immune regulation and is merely an effect of the cross-talk between CD4+ T cells and fibroblasts (see Figure 1). The gene discussed is CD274; the disease is pulmonary fibrosis.