Transforming growth factor‑β1 (TGF-β1) is the primary member of the large transforming growth factor-β (TGF-β) family which have crucial roles in multiple processes including cell proliferation, development, wound healing and immune responses. Abnormality of TGF-β function has been implicated in multiple human diseases, including fibrosis, autoimmune diseases and cancer. TGF-β1 is synthesized and secreted in a latent, inactive complex, which contains dimerized non-covalently associated TGF-β1growth factor domain and a large prodomain, the latency associated peptide (LAP). LRRC33, a homologous protein of the pro-TGF-β1 binding protein GARP (LRRC32), is covalently linked to the prodomain of TGF-β1, and highly expressed microglia cells in the central nervous system (CNS) where LRRC33 associates with pro-TGF-b1 and regulates TGF-β1 function.