This treatment was therefore considered responsible for the donorspecific hyporeactivity by in vitro one-way MLR and may be required for the maintenance of tolerance to allografts as supported by the significantly higher FoxP3 mRNA expression in the long-term accepted allografts than in the rejected allografts. Our results are consistent with those of other, supporting the conclusion that Tregs is critical to the maintenance of allograft survival. These results conflict with published data, which state that longterm calcineurin inhibitors are associated with a decline of Tregs in patients receiving solid organ transplantation. Considering the complex process of tolerance induction/maintenance to transplanted tissues and the relatively delayed appearance of donor-specific FoxP3+ Tregs in group 5, we deduce that the increased donor-specific FoxP3+ Tregs are likely to be induced by the myeloid chimerism established in intact allogeneic hind limb recipients under the minimally toxic CsA guarantee. However, this has yet to be confirmed. There are also data indicating that the effects of calcineurin inhibition on Treg function may be dose-dependent and that low doses may permit or even support Treg function. We used a noninvasive laser Doppler flowmeter to monitor postoperative blood perfusion status. No significant differences were observed between any 2 groups that received the same treatment, indicating that the B–R procedure did not affect blood perfusion. Isotransplantation and rejection groups showed the same survival period, confirming that this procedure does not cause the final rejection of B–R allografts observed in the experimental groups. In conclusion, using B–R hind limbs with all the same elements as the intact hind limbs PI-103 except for its lack of bone components, we observed that, under a minimally toxic recipient immunosuppressive protocol, intact allogeneic hind limbs were able to survive rejection-free for more than 100 days. When the bone components were removed, early rejection episodes and graft loss were observed. Further investigation indicated that donor-specific FoxP3+ Tregs are required for donor hyporeactivity in in vitro one-way MLR and that they may be responsible for long-term allograft survival. The means by which these cells are generated merits further investigation. The B–R hind limb model might serve as a counterpart to tolerance induction studies of hind limb allotransplantation and so advance realization of the allotransplantation in clinical settings. Long-term use of antiretroviral therapy in HIV-positive persons may be challenged by the need for high-level adherence, development of drug resistance, toxicities, and cost. Treatment strategies conferring durable virological control, whilst minimising ART exposure are highly desirable. With this goal in mind, strategic interruption of ART was the focus of several studies. However, interruption of ART is no longer a recommended strategy and the level of HIV plasma viral load following ART stop has been shown to reach levels comparable to pretreatment values, increasing onward transmission risk. Inaccessible reservoirs of latently-infected resting memory CD4 Tcells are hypothesised to be the major source contributing to viraemia rebound after stopping ART. Recent research has shown the dramatic effect of ART to prevent onward viral transmission, and mathematical models predict that it may potentially be possible to eliminate HIV infection at a population level with universal treatment coverage for all HIV-positive individuals, irrespective of CD4 count.