CD4 and pulmonary fibrosis: Given that FICZ enhanced the accumulation of CD4+Foxp3+ Tregs in the lungs of BLM-treated mice during the inflammatory phase only and that BLM induced the accumulation of CD4+Foxp3+ Tregs in this lung fibrosis model (Fig. 6c), increasing the number of protective Tregs during the inflammatory phase with FICZ as shown in the present study may lead to weaken the inflammation and result in the alleviation of pulmonary fibrosis.