Absolute of CD4 ⁺CD25 ⁺FOXP3 ⁺ regulatory T-cell count rather than its ratio in peripheral blood is related to long-term survival of renal allografts

CD4 ⁺CD25 ⁺Foxp3 ⁺ regulatory T cells (Tregs) may reflect the immune status of kidney transplant (KTx) recipients. Since individual KTx recipients show different lymphocyte counts, we hypothesized that the Treg absolute count rather than its peripheral ratio was more related to long-term survival. We enrolled 42 patients with more than 5-year KTx survival: 32 patients with stable graft function and 10 suffering chronic rejection (CR group). The stable group was divided into four subgroups according to graft survival time: subgroups A (56 years); B (67 years); C (78 years); and D (>8 years). Healthy volunteers were enrolled as controls. We compared the peripheral ratio and absolute count of CD4 ⁺, CD4 ⁺CD25 ⁺, and CD4 ⁺CD25 ⁺Foxp3 ⁺ Tregs. Treg peripheral ratio was not significantly different among the three groups. However, the Treg absolute count was higher among the stable than the CR group (P <.01). Meanwhile, both Treg ratios and absolute counts were altered with renal graft survival. Treg absolute count in subgroups B and C were not only higher than that in subgroup A (P <.05), but also was significantly higher than that in the CR control group or (P <.05). Interestingly, both the Treg ratio and absolute count in subgroup D were lower than those in subgroups B and C (P <.05). Treg quantitation, which alters with graft survival time, may contribute to long-term acceptance of renal allografts. Compared to Treg peripheral ratio, the absolute count may be a superior index to estimate KTx recipient immune status.