TGFB1 and systemic lupus erythematosus: In this sense, the TGFB1 (rs1800470) variant is independently associated with susceptibility, TGF-β1 plasma levels, and biological activity in patients with SLE [8] and patients that carry certain haplotypes of the FOXP3 (forkhead box protein P3) gene have higher TGF-β1 levels [9].