There is increasing evidence that various maturational stages of B-cells infiltrate various solid organ transplants undergoing acute rejection. The presence of immature CD20+ and mature CD138+ plasma cells associate with more aggressive and steroid-recalcitrant graft rejection and portend poor graft outcomes. Though associative, the causal role of B-cells in graft rejection remains to be better understood. This review discusses the possible roles of B-cells in graft rejection, whether involved as antigen presenting, as indirect effector, or antibody producing cells.