Functional characterization of CD4⁺CD25⁺ T cells in patients with symptomatic MC. (A) The blood CD4⁺CD25⁺ population was immunomagnetically sorted (25⁺) in 3 untreated patients with symptomatic MC, and assayed for its capacity to suppress anti-CD3 anti-CD28-mediated autologous responder cell (25^-) proliferation at a 1:1 ratio, in the presence or absence of exogenous IL-2. Histograms represent the median of triplicates. Percent inhibition of proliferation is indicated. (B) Proliferative response of CD4⁺CD25⁺ T cells on anti-CD3 anti-CD28 activation, in the presence or absence of exogenous IL-2.