[Show abstract][Hide abstract] ABSTRACT: The critical roles of TGF-β in the reciprocal differentiation of tolerance-promoting CD4(+)Foxp3(+) regulatory T cells (Tregs) and proinflammatory Th17 effector cells affect alloimmune reactivity and transplant outcome. We reasoned that a strategy to harness TGF-β and block proinflammatory cytokines would inhibit the differentiation of Th17 cells and strengthen the cadre of Tregs to promote tolerance induction and long-term allograft survival. In this study, we report the development of a long-lasting autoactive human mutant TGF-β1/Fc fusion protein that acts in conjunction with rapamycin to inhibit T cell proliferation and induce the de novo generation of Foxp3(+) Treg in the periphery, while at the same time inhibiting IL-6-mediated Th17 cell differentiation. Short-term combined treatment with TGF-β1/Fc and rapamycin achieved long-term pancreatic islet allograft survival and donor-specific tolerance in a mouse model. This effect was accompanied by expansion of Foxp3(+) Tregs, enhanced alloantigen-specific Treg function, and modulation of transcript levels of Foxp3, IL-6, and IL-17. Our strategy of combined TGF-β1/Fc and rapamycin to target the IL-6-related Tregs and Th17 signaling pathways provides a promising approach for inducing transplant tolerance and its clinical application.
Full-text · Article · Oct 2010 · The Journal of Immunology
[Show abstract][Hide abstract] ABSTRACT: Recent studies have demonstrated that in peripheral lymphoid tissues of normal mice and healthy humans, 1% to 5% of alphabeta T-cell receptor-positive (TCR(+)) T cells are CD4(-)CD8(-) (double-negative [DN]) T cells, capable of down-regulating immune responses. However, the origin and developmental pathway of DN T cells is still not clear. In this study, by monitoring CD4 expression during T-cell proliferation and differentiation, we identified a new differentiation pathway for the conversion of CD4(+) T cells to DN regulatory T cells. We showed that the converted DN T cells retained a stable phenotype after restimulation and that furthermore, the disappearance of cell-surface CD4 molecules on converted DN T cells was a result of CD4 gene silencing. The converted DN T cells were resistant to activation-induced cell death (AICD) and expressed a unique set of cell-surface markers and gene profiles. These cells were highly potent in suppressing alloimmune responses both in vitro and in vivo in an antigen-specific manner. Perforin was highly expressed by the converted DN regulatory T cells and played a role in DN T-cell-mediated suppression. Our findings thus identify a new differentiation pathway for DN regulatory T cells and uncover a new intrinsic homeostatic mechanism that regulates the magnitude of immune responses. This pathway provides a novel, cell-based, therapeutic approach for preventing allograft rejection.