Impact of regulatory T cells on engraftment and quantitative immune reconstitution. (A) Peripheral blood with normal total white blood cells (WBCs) in animals on day 40 after transplantation. Analysis of subpopulations of WBCs showed abnormally low numbers of lymphocytes (Lymph) and high numbers of neutrophils (ANC) in recipients of Tcons alone, the latter accounting for the increased total WBC. Animals that received Tregs with Tcons had normal levels of ANC and enhanced numbers of lymphocytes. Peripheral blood reconstitution of total lymphocytes and lymphoid subsets on days 14 (B-F) and 40 (G-K) after transplantation. Statistical differences (*P < .05) were noted between Tcons versus Tcon + Treg recipients in total lymphocytes, CD4⁺, CD8⁺, and NK⁺ cells on day 14. Differences were more significant on day 40 and included CD19⁺ cells. Results represent the mean plus or minus SE (3 to 4 mice per group, one of 3 experiments).