Role of alloreactive T cell in clonal deletion and regulatory T cells in transplant tolerance / 中国免疫学杂志

ABSTRACT

Objective:To investigate the role of alloreactive T cell in clonal deletion and regulatory T cells ( Treg) in transplant tolerance.Methods:F1 mice were bred by crossing female BALB/c mice and male C57BL/6 mice.Within 24 h,newborn C57BL/6 mice were inoculated with F1 spleen cells via the orbital branch of the anterior facial vein.Six weeks later,the mice were subjected to F1 skin grafting to evaluate their tolerance.Proliferation,flow cytometry and adoptive transfer assay were used to analyze clonal deletion of alloreactive T cells and the expression of CD4+Foxp3+T cells in neonatal treated mice.Results: Newborn C57BL/6 mice injected with F1 splenic cells could induce transplantation tolerance,the level of tolerance was associated with the dose of splenic cells.3×107 splenic cells from F1 mice could induce long-term skin graft acceptance in C57BL/6 mice ,1×107splenic cells significantly prolonged the survival of F1 skin grafts,but the grafts completely rejected within 50 days.The mixed lymphocyte reaction ( MLR) experiment in vivo showed that alloreactive T cell in long-term tolerant mice was deleted completely,but a certain amount of reactive T cells existed in the low-dose group mice.Flow cytometry ( FCM) analysis showed that the expression of CD4+Foxp3+T cell in the high-dose group and low-dose group mice had no obvious difference compared with the naive mice.When alloreactive T-cells were injected into tolerant mice,the skin graft rejection was observed,and Treg cells upregulated in graft-rejected mice.Conclusion:The degree of transplantation tolerance depended on the clonal deletion of alloreactive T cells,instead of on the expression of CD4+Foxp3+Treg cells.CD4+Foxp3+regulatory T cells upregulated in graft rejected mice,which may be served as a negative feedback mechanism to control the intensity of rejection.