B-1 cell participation in T-cell-mediated alloimmune response.

B-1 and B cells are important producers of natural antibodies in mice and humans and, therefore, are considered as the first line of defense against pathogens. Because of that, their role in T-cell-mediated immune responses is commonly underrated. However, recent studies have described the participation of B-1 cells in immediate and delayed-type hypersensitivity. The present work assessed the role of B-1 cells in the rejection of allografts in mice, an immune reaction mainly orchestrated by T cells. We have transplanted allogeneic skin and heart to wild-type and B-1-cell-deficient mice, and followed rejection kinetics. Skin graft-infiltrating cells were analyzed by flow cytometry. We observed a delay in rejection kinetics of B-1-cell-deficient mice when compared to wild-type mice. Adoptive transfer of B-1 cells into B-1-cell-deficient mice abrogated this delay. The longer survival observed in the absence of B-1 cells correlated with less CD8+ T cells infiltrating the grafts, as well as with more mast cells. Collectively, our results show the participation of B-1 cells in the allograft rejection process in mice and collaborate to the understanding of B-1 cell biology.