Short-term anti-CD25 monoclonal antibody administration down-regulated CD25 expression without eliminating the neogenetic functional regulatory T cells in kidney transplantation

CD4(+)CD25(+) forkhead box P3 (FoxP3)(+)regulatory T (T-reg) cells are generated and play a key role in the induction and maintenance of transplant tolerance in organ recipients. It has been proposed that interleukin (IL)-2/IL-2 receptor (IL-2R) signalling was essential for the development and proliferation of antigen-activated T cells that included both effector T cells and T-reg cells. Basiliximab (Simulect (TM)), a chimeric monoclonal antibody directed against the alpha-chain of the IL-2R (CD25), can be expected to not only affect alloreactive effector T cells, but also reduce the number and function of T-reg cells. We therefore examined the effect of basiliximab induction therapy on the number and function of the T-reg cells in renal recipients. Basiliximab decreased the percentage of CD4(+)CD25(+)T cells, but failed to influence the percentage of CD4(+)FoxP3(+) T-reg cells. The cellular CD25 expression was decreased significantly by basiliximab injection, but CD4(+)CD25(+) T cells was not depleted from the circulating pool through monoclonal antibody activation-associated apoptosis. Functional analysis revealed that inhibitory function of T-reg cells from recipients with basiliximab injection was not significantly different from recipients without injection. These data indicate that the functional T-reg population may not be influenced by short-term basiliximab treatment.