In mice, there has been increasing evidence that FOXP3-expressing CD4+CD25+ regulatory T cells (Tregs) inhibit potentially reactive T cells to allo-antigens and play an important role in transplant (Tx) tolerance. Human CD4+CD25 high+ T cells represent Tregs, characterized by anergic and antigen-specific suppressive properties. Despite the significance of miniature swine as a preclinical model, only limited data are available regarding the existence of a porcine counterpart to the murine or human Tregs. Methods: From peripheral blood of five adult miniature swine, CD4+ cells (CD4+), CD4+CD25 high+ cells (CD25high+), CD4+CD25low+ cells (CD25low+), and CD4+CD25- cells (CD25-) were isolated with a cell sorter. Expression of the homologous gene to murine FOXP3 was quantified by RT-PCR in isolated fractions, and normalized to GAPDH. Proliferation of CD25high+ and suppressive property of CD25high+ to CD4+ responder cells upon allogeneic stimulation was evaluated by MLR and dilution assay, respectively, after isolation and 9-day culture with allogeneic cells in the presence of IL-2. Results: FOXP3 was expressed ten times higher in CD25 high+, compared to that in CD25low+ (p<0.05). CD25- expressed almost no FOXP3. CD25high+ was anergic and could suppress the proliferation of responder CD4+ upon allogeneic stimulation after isolation. After culture, CD25high+ remained anergic and showed a more suppressive effect on cells used for culture than on third party cells. Conclusions: 1) CD25high+ in miniature swine peripheral blood expressed an extremely high level of FOXP3. 2) This fraction was anergic and has suppressive properties, showing antigen-specificity after exposure to alloantigens. 3) We found for the first time that miniature swine CD25high+ represents the homologous population to the murine and human Tregs. Miniature swine Tx models, therefore, may provide opportunities for pre-clinical evaluation of innovative Tregs-based tolerance strategy.
Regulatory T Cells Are Resistant to Cyclophosphamide (Cy) Through Expression of Aldehyde Dehydrogenase (ALDH) Upon Allogeneic Stimulation