The evolutionarily conserved TGF-beta proteins are distributed ubiquitously throughout the body and have a role in almost every biological process. In immunity, TGF-beta has an important role in modulating immunity. Much is understood about the process of TGF-beta production as a latent molecule and of the consequences and the intercellular signaling of active TGF-beta binding to its receptors; however, there is little discussed between the production and activation of TGF-beta. This review focuses on what is understood about the biochemical and physiological processes of TGF-beta activation and identifies the gaps in understanding immune cell activation of TGF-beta. A mechanistic understanding of the process activating TGF-beta can lead to regulating multiple biological systems by enhancing or inhibiting TGF-beta activation.