CD40-CD40L costimulation blockade induced the tolerogenic dendritic cells in mouse cardiac transplant.

We aimed to investigate whether tolerogenic dendritic cells (DCs) were induced in the tolerant recipients with the blockade of CD40-CD40L costimulation. Mouse heterotopic heart transplantation was performed. DCs were sorted from rejected and tolerant recipients using magnetic-activated cell sorting. Their expression of CD40, CD80, and CD86 was examined using fluorescence-activated cell sorting. DCs were stimulated with lipopolysaccharide in vitro, and interleukin 10 (IL-10) and IL-12 levels in the supernatants were evaluated using enzyme-linked immunosorbent assay. By using mixed leukocyte reaction, we investigated the stimulatory capacities and tolerogenic capability of DCs. DCs from tolerant recipients expressed lower level of costimulatory molecules, including CD40, CD80, and CD86 and released higher levels of IL-10 and lower levels of IL-12. In addition, DCs from tolerant recipients were weak stimulators of the mixed leukocyte reaction and inhibited the proliferation of splenocytes. IL-10(high)IL-12(low) DCs with immature phenotype were induced in the tolerant recipients with the blockade of CD40-CD40L costimulation, and they obtained the tolerogenic function.

Expansion of CD25+CD4+ regulatory T cells by natural mature dendritic cells.

Because of the anergy of CD25+CD4+ regulatory T cells, it is unclear how the number of these regulatory T cells is sustained and expanded in normal physiologic circumstances. In the present study, we examined the effect of natural allogeneic mature dendritic cells (DCs) on the proliferation and function of CD25+CD4+ T cells. Our data showed that natural allogeneic mature DCs stimulated CD25+CD4+ T-cell growth vigorously, whereas immature DCs had little effect on the proliferation of CD25+CD4+ T cells. After expansion by mature DCs, CD25+CD4+ T cells maintained their expression of Foxp3 and suppressed the proliferation of CD25- CD4+ T cells similar to freshly isolated CD25+CD4+ T cells. Our results introduce a potentially critical role played by natural allogeneic mature DCs, which exist in normal physiologic circumstances, in controlling CD25+CD4+ regulatory T-cell expansion and function.

Transplant long-surviving induced by CD40-CD40 ligand costimulation blockade is dependent on IFN-γ through its effect on CD4(+)CD25(+) regulatory T cells.

BACKGROUND: IFN-γ was documented to be commonly associated with acute rejection. In the present study, we investigated the role of IFN-γ in the transplant long-surviving induced by blocking CD40-CD40 ligand (CD40-CD40L) costimulation and its mechanisms. METHODS: IFN-γ expression in cardiac allografts and spleens from syngeneic and allogeneic recipients with or without anti-CD40L monoclonal antibody (MR-1) treatment was examined by real-time RT-PCR. The grafts survival time in Wild type (IFN-γ(+/+)) and IFN-γ deficient (IFN-γ(-/-)) recipients was investigated. Mixed lymphocyte reaction (MLR) of CD4(+) T cells and cytotoxic T lymphocyte (CTL) assay of CD8(+) T cells were also studied. FoxP3 expression in allografts and spleens from IFN-γ(+/+) or IFN-γ(-/-) recipients with MR-1 treatment was examined. Furthermore, FoxP3, IL-10 and CTLA-4 expressions and the suppressive capability of CD4(+)CD25(+) regulatory T cells were examined. RESULTS: Rejected allografts showed significantly higher IFN-γ expression than long-surviving allografts. Allograft survival was not prolonged in nonimmunosuppressed IFN-γ(-/-) mice. Administration of MR-1 induced long-term survival in 90.1% of IFN-γ(+/+) recipients (98±6.6 days) but failed to do so in IFN-γ(-/-) group (16.2±4.0 days). IFN-γ(-/-) recipients facilitated the proliferation and CTL generation of T cells. The allografts and spleens from IFN-γ(+/+) recipients contained higher FoxP3 expression than IFN-γ(-/-) recipients. Moreover, CD4(+)CD25(+) T cells from IFN-γ(+/+) recipients displayed a higher FoxP3 and IL-10 expression and suppressive capability. CONCLUSION: IFN-γ plays an important role in the long-surviving induced by blocking CD40-CD40L through inhibiting the function of activated T cells and increasing suppressive capability of CD4(+)CD25(+) regulatory T cells.