Recovering lymphocytes are mostly CD3⁺CD4⁺, and there is a much larger than expected population of CD3⁺CD4⁺CD25⁺Foxp3⁺ T cells. Flow cytometric analysis of peripheral blood lymphocytes isolated from patients during the early phase of lymphocyte recovery after induction chemotherapy showed that there is significant recovery of CD3⁺CD4⁺ and CD3⁺CD8⁺ cells. Data from 1 representative patient are shown on the left. CD3⁺ cells constituted a median of 73.4% (range, 19%-93%) of the recovering mononuclear cells. Of CD3⁺ cells, CD8⁺ cells constituted a median of 16.7%, whereas CD4⁺ cells constituted a median of 66.4%. Surprisingly, there also was a rapid and significant recovery of regulatory T cells (median, 10.5% of CD4⁺ T cells), which were phenotypically identified by the coexpression of CD3, CD4, CD25, and Foxp3.