Abstract The humoral response mediated by alloantibodies directed against donor HLA molecules (DSAs) is one of the main causes of graft loss in kidney transplantation. Understanding the pathophysiology leading to humoral kidney rejection as the development of therapeutic tools is therefore a main objective in the field of solid organ transplantation and necessitate adapted experimental models. Among the immunosuppressive agents used in renal transplantation, belatacept, a fusion protein targeting T costimulatory molecules has shown its ability to prevent more efficiently the secretion of DSA by different mechanisms including a direct action on plasma cells but also on B lymphocytes and follicular helper T lymphocytes (Tfh) cooperation. This cellular cooperation occurs within germinal centers (GC), the seat of B lymphocytes differentiation. Here, we aimed to develop a dedicated mouse model in which human GC would be functional to study the effect of belatacept on GC formation and the ability of B lymphocytes to secrete immunoglobulin. We next demonstrate that belatacept inhibits the formation of these GCs, by inhibiting the frequency of Tfh and B lymphocytes. This alters the B maturation and therefore the generation of plasma cells and consequently, immunoglobulin secretion.