This study demonstrated that fucoidan administration in irradiated mice attenuated cytokine (TIMP-1, CXCL1, MCP-1, MIP-2, and IL-1Ra) expression in the collected pleural fluid and reduced pleural fluid-induced collagen expression in fibroblasts, which were correlated with the reduction of neutrophil and macrophage infiltration in lung tissues; macrophage and neutrophil infiltration may lead to RP and RT-induced lung fibrosis (Figure 6). This evidence concerns the gene TIMP1 and pulmonary fibrosis.