Low-dose IL-2 induces the expansion of FOXP3^-CD56⁺ cells in vivo. (A) Percent change in frequencies of CD56⁺ cells in total blood lymphocytes was determined using values obtained by flow cytometry from samples collected before and during IL-2 treatment. Values for one patient (number 11) were not available. (B) CD4⁺ T cells and CD3^-CD56⁺ NK cells were purified by cell sorting from 5 patient samples collected during IL-2 treatment. FOXP3 expression was assessed by quantitative PCR in both cell subsets for the 5 patients.