Role of B cells in CD45RB antibody-induced transplantation immune tolerance

AIM: To investigate the role of B cells in CD45RB antibody-induced transplantation immune tolerance. METHODS: Single cell suspension was made from the spleen of BALB/c nude mice disposed by CD45RB antibody, then mixed cultured with T cells of BALB/c mice and spleen cells of C57BL/6 mice. The Th1, Th2, Treg and Tm cells were monitored by flow cytometry during the culture process. The skin graft model was set up with B6.μMT^-/- mice as receptors and BALB/c mice as donors. CD45RB antibody was intraperitoneally injected into the receptors after transplantation and then CD3⁺CD45RB^hi cells were detected by flow cytometry. In another mixed lymphocyte culture, CD45RB antibody was added, and then B cells were isolated and injected into B6.μMT^-/- mice through the tail vein. The heart transplantation model was established with B6.μMT^-/- mice as receptors and BALB/c mice as donors, and then the survival and the migration of B cells to the thymus were observed. RESULTS: When T lymphocytes were co-cultured with B lymphocytes treated with anti-CD45RB monoclonal antibody(mAb) in vivo, the percentages of Th2 and Treg cells were up-regulated and Th1 cells were down-regulated, but Tm cells were not altered as compared with the control. In vivo without B lymphocytes, anti-CD45RB mAb also down-regulated the expression of CD45RB in T lymphocytes. The reduction was faster and the percentage of CD3⁺CD45RB^hi T cells was not altered as compared with the control. The B lymphocytes treated with anti-CD45RB mAb in vitro prolonged the lifetime of receptor in heart transplantation model but failed to induce complete tolerance. After recieving B cells treated with anti-CD45RB mAb and allogeneic heart transplantation, B cells migrated to the thymus in B6.μMT^-/- mice. CONCLUSION: B lymphocytes play a definite role in the transplantation immune tolerance induced by anti-CD45RB mAb through their affection on T-cell subgroups and also in the central tolerance. However, the induction of immune tolerance can not only rely on B cells.