Inverse correlation of CD25^highFOXP3⁺CD4⁺ Tr frequency and CD4⁺ T-cell proliferative response to mIg-pulsed DCs. (Top) Decreased frequencies of CD25^highFOXP3⁺CD4⁺ Tr among peripheral CD3⁺ T-lymphocytes (x-axis) correlated with increased proliferative response to mIg-pulsed DCs for the individual MM patient (x- and y-values for patient nos. 1-10 and a trendline are plotted). The mean percentage of dividing CD4⁺ T cells after 7 days of coculture with mIg-pulsed DCs is shown (y-axis). Corresponding mean Tr frequency of 7 control donors was 2.1% (SD, 0.9%). (Bottom) Suppression of CD4⁺ T-cell proliferative response to mIg-pulsed DCs during coculture in the presence of autologous Tr. As in Figure 6, the 100% value on the y-axis depicts the proliferation of CD4⁺ T cells without Tr present (1:0). Proliferation assessed at increasing concentration of Tr (1:0.25, 1:0.5, 1:1) is expressed as a percentage (± SD, triplicate cultures) of maximal response. The results of DC cocultures with sorted CD4⁺ T-cell populations from 4 patients are shown. Due to limited cell sorting yield of Tr, it was not possible in all experiments to assess proliferation at every ratio indicated (x-axis).