Interestingly, the “window of opportunity” for the regulation of CD8+ T-cell responses by Treg overlapped with the time of CD25 expression on CD8+ T-cells: depletion of Treg cells as late as d2–3 post infection enhanced antigen-specific T-cell numbers in a viral infection model, but depletion later than d5 (when CD8+ T-cells do not express CD25) failed to do so (Kastenmuller et al., 2011). This evidence concerns the gene IL2RA and viral infectious disease.