The reduction is most striking in CD45RBhigh naive T cells (~16-fold change) and is less so in CD25+CD4+ T cells (3–4-fold change) in 2–3 months old, day-3 thymectomised mice, which have relatively higher percentages of CD25+ or Foxp3+ Tregs.14, 15, 16 These CD25+ Tregs are as ‘regulatory' as those from non-treated wild-type mice in suppressing the development of colitis by cell transfer of CD45RBhigh T cells into Rag2−/− mice.14 Here, CD4 is linked to colitis.