Human CD4+CD25low adaptive T regulatory cells suppress delayed-type hypersensitivity during transplant tolerance.

Adaptive T regulatory (T(R)) cells mediate the suppression of donor-specific, delayed-type hypersensitivity (DTH) in tolerant organ transplant recipients. We hypothesized that cells belonging to the CD4(+)CD25(+) T cell subset but distinct from natural T(R) cells may fulfill this role. To test this hypothesis, PBMC and biopsy samples from two tolerant kidney transplant recipients (K1 and K2) were analyzed. When transferred with recipient APC into a SCID mouse footpad, CD4(+) T cells were hyporesponsive in DTH to donor type HLA-B Ags and derivative allopeptides. However, anti-human TGF-beta1 Ab revealed a response to immunodominant allopeptides in both patients, suggesting that CD4(+) T effector (T(E)) cells coexisted with suppressive, TGF-beta1-producing CD4(+) T(R) cells. During in vitro culture, allopeptide stimulation induced both IFN-gamma-producing and surface TGF-beta1(+) T cells. The relative strength of the latter response in patient K1 was inversely correlated with the level of systemic anti-donor DTH, which varied over a 6-year interval. Allopeptide-induced surface TGF-beta1 expression was found primarily in Forkhead box P3 (FoxP3)-negative CD4(+)CD25(low) T cells, which could adoptively transfer suppression of donor-specific DTH. Biopsy samples contained numerous surface TGF-beta1(+) mononuclear cells that costained for CD4 and, less frequently CD25, but were negative for FoxP3. The CD4(+)TGF-beta1(+) T cells were localized primarily to the tubulointerstitium, whereas TGF-beta1(-)FoxP3(+)CD25(+) cells were found mainly in lymphoid aggregates. Thus, adaptive T(R) cells suppressing T(E) cell responses to donor allopeptides in two tolerant patients appear to be functionally and phenotypically distinct from CD4(+)CD25(high)FoxP3(+) T cells.

Piceatannol in combination with low doses of cyclosporine A prolongs kidney allograft survival in a stringent rat transplantation model.

BACKGROUND: The discovery of new immunosuppressive agents has enhanced short-term graft survival. However, current immunosuppressants often induce toxicities that limit their clinical use. Thus, there is a need for new immunosuppressants for use in clinical transplantation. Piceatannol blocks Syk and ZAP-70, tyrosine kinases involved in immune cell activation. We examined whether piceatannol prolongs kidney allograft survival in the stringent ACI-to-Lewis rat model. METHODS: Kidney recipients were divided into four groups. Group 1 (n=8) received piceatannol 30 mg/kg per day intravenously and cyclosporine A (CsA) 2 mg/kg per day intramuscularly from day -3 to day 7 after transplantation. At day 8, piceatannol was reduced to 10 mg/kg per day and the combined treatment continued until day 60. Group 2 (n=9) received 2 mg/kg per day CsA alone from day -3 to day 60. Group 3 (n=4) received piceatannol alone as in group 1. Group 4 (n=2) received only the vehicle dimethyl sulfoxide from day -3 to day 60. Graft rejection was defined as either a serum creatinine level more than 2 mg/dL or animal death. RESULTS: Group 1 animals survived for at least 115 days (n=8, P<0.05), with several animals maintaining their grafts for more than 200 days. In contrast, 8 of 9 animals in group 2 rejected their grafts within 10 days of transplantation; one animal survived for 71 days. Excellent graft function was maintained in group 1 animals despite withdrawal of immunosuppression. CONCLUSIONS: These results are the first to show that piceatannol, when combined with subtherapeutic dosages of CsA, prevents graft rejection, suggesting that targeting Syk and Zap could be useful for preventing graft rejection.