The ability of a host to generate an appropriate immune response is critical to provide protection against a particular pathogen and to provide long-lasting memory against future reinfection. However, this immune response must be tightly regulated to prevent its persistence or inadequate activation which can lead to the development of immune pathologies. Mammalian immune system comprises a wide array of immune cells and molecules. In particular, the ability ofimmune cells to secrete and respond to cytokines is central to the orchestration of immune responses. My PhD project has focused on the role of a particular cytokine named Transforming Growth Factor β (TGFβ). Unlike most other cytokines, TGFβ is secreted in a latent form and must be activated to bind its receptor and induce response on target cell. Our team and others have shown that αvβ8 integrin plays a critical role in TGFβ activation and thus the regulation of TGFβ-dependent immune responses. More precisely, I investigated the role of αvβ8 integrin in the regulation of intestinal immunityand humoral B cell responses. In particular, my work focused on three immune processes: 1/ the induction of TREG and TH17 in Mucosal Associated Lymphoid Tissues and 2/ the regulation ofintestinal IgA humoral responses and 3/ the regulation of T-dependent B cell responses during the germinal center reaction.