Description: Activin A is a member of the TGF-β superfamily, along with the other activin proteins and the structurally related inhibins. The activins are dimeric proteins formed by the association of two of the four existing β subunits, βA, βB, βC, and βE. These subunits are shared with the inhibin proteins, which are heterodimers of one β and one α chain. Activin A is a homodimer of two 13 kDa βA subunits, which can also associate with βB or βC to form Activin AB or AC, respectively. Activin A is expressed by various cell types and exhibits pleiotropic effects including the regulation of metabolism, homeostasis, cell proliferation and differentiation, apoptosis, and tissue healing. Activin A has been recently reported to work in synergy with TGF-β to promote the induction of antigen specific iTreg cells leading to inhibition of Th1 and Th2-mediated responses.