[Impact of novel negative immunoregulatory dendritic cells on regulatory T cells in cardiac allograft recipient rats].

AIM

To investigate the effect of recipient dendritic cells (DC) loaded with PUVA-treated donor splenic lymphocytes (PUVA-SP) on CD4(+) CD25(+) regulatory T cells (Treg) and the survival time of cardiac allograft in rats.

METHODS

Cardiac allografts from DA donor rats were transplanted into LEW recipient rats. Donor splenic lymphocytes were treated with 8-methoxypsoralen plus UVA irradiation (PUVA). Recipient bone marrow-derived DCs were co-cultured with PUVA-treated donor splenic lymphocytes (PUVA-SP) and the phenotype of the treated DCs was analyzed with flow cytometry. Seven days before transplantation, recipients were given infusion of recipient DCs loaded with PUVA-treated donor splenic lymphocytes (PUVA-SP DC) through the peripheral vein. The cardiac allograft survival time was evaluated by palpation every day. The frequency of CD4(+)CD25(+) T cells and CD4(+) CD25(high) T cells and their Foxp3 expression were analyzed using flow cytometry. Fourteen days after transplantation, T lymphocytes of the recipient rats receiving PUVA-SP DC were transferred to the normal LEW rats. The delayed type hypersensitivity (DTH) of the transferred LEW rats to the donor DA rats antigen then was measured.

RESULTS

After co-cultured with PUVA-SP, recipient DCs still maintained an immature phenotype with low levels of MHC II, CD80 and CD86. The injection of PUVA-SP DCs significantly increased the frequencies of CD4(+)CD25(+) T cells and CD4(+) CD25(high) T cells and the expression of Foxp3 in the peripheral blood, and prolonged the allograft survival time. The donor antigen specific hyporesponsiveness could be transferred to normal LEW rats through adoptive transfusion.

CONCLUSION

PUVA-SP DCs effectively up-regulate CD4(+) CD25(+) Foxp3(+) Treg and induce donor antigen specific hyporesponsiveness, thus prolonging the allograft survival time.