IL2 and lymphopenia: Therefore, in both low- and high-dose injected hosts, the IL-2 produced by conventional T cells during lymphopenia-induced proliferation is expected to be efficiently sequestered by either the minor fraction of contaminants CD25+Foxp3+ or CD25−Foxp3+ cells that had upregulated CD25 expression after proliferation, leading to the expansion the regulatory T cell numbers to a normal amount, likely sufficient to control colitis.