TGFB1 and autoimmune disease: Fetal liver MSC-EXs transport latency-associated peptides, TGF-β, and thrombospondin 1 to activate TGF-β/Smad2/3 signaling in natural killer (NK) cells and they also inhibit NK cell cytotoxicity in vitro, which implies a potential for the treatment of autoimmune diseases [79].