Transforming Growth Factor-β/Interleukin-2–induced Regulatory CD4 + T Cells Prolong Cardiac Allograft Survival in Rats

Treatment of naive CD4 + T cells in vitro with transforming growth factor-β (TGF-β) or TGF-β/interleukin-2 (IL-2), combined with stimulation in a mixed lymphoid culture (MLC), has been shown to generate CD4 + CD25 + regulatory T cells. However, little is known about the effect of these regulatory T cells on cardiac allograft survival in vivo. CD4 + CD25 + T cells were generated from Lewis (LEW) rat spleen through a primary MLC with TGF-β (10 ng/ml) or TGF-β/IL-2 (10 U/ml). The effect of adoptive transfer of the CD4 + CD25 + T cells (5.0 × 10 7) was evaluated using an animal model of ACI rat cardiac allograft survival in LEW recipients. The MLC with TGF-β or TGF-β/IL-2 generated CD4 + CD25 + regulatory T cells, which suppressed the cytotoxic activity of LEW spleen T cells against irradiated ACI spleen cells in vitro. Adoptive transfer of the CD4 + CD25 + regulatory T cells intravenously to naive syngeneic recipients significantly prolonged the ACI cardiac allograft survival ( N = 6, 13.5 ± 3.4 days) compared with the control group ( N = 6, 5.0 ± 0.6 days). Intravenous administration of CD4 + CD25 + regulatory T cells, successfully generated by TGF-β/IL-2 treatment, had a significant effect on cardiac allograft survival in this rat model. Adoptive transfer of regulatory T cells may represent a novel approach for preventing allograft rejection.