The arginine-glycine-aspartate (RGD)-binding integrins αvβ6 and αvβ8 activate latent TGFβ1 and TGFβ3 in vivo, but it is uncertain whether other RGD-binding integrins such as integrins αvβ5 and αvβ3 activate these TGFβ isoforms. To define the combined role of αvβ6- and αvβ8-integrin in TGFβ activation, we analyzed mice lacking function of both integrins by means of gene deletion and/or pharmacologic inhibition. Most Itgb6^–/–;Itgb8^–/– embryos die at mid-gestation; those that survive develop cleft palate–as observed in Tgfb3^–/– mice. Itgb8^–/– mice treated with an anti-αvβ6-integrin antibody develop severe autoimmunity and lack Langerhans cells–similar to Tgfb1-null mice. These results support a model in which TGFβ3-mediated palate fusion and TGFβ1-mediated suppression of autoimmunity and generation of Langerhans cells require integrins αvβ6 and αvβ8 but not other RGD-binding integrins as TGFβ activators.