IL33 and pulmonary fibrosis: In addition, decreased expression of the soluble form of ST2 (55 kDa), the receptor of IL-33, and decreased phosphorylation of AKT (S742) protein were found in the lung tissue of mice with BLM-induced lung fibrosis, indicating that lung tissue cells were affected by circulating IL-6 and IL-33 during lung fibrosis (Figure 5(b)).