Isolation of KLH- or PA-specific T cell clones. (A) T cell cultures from Donor #2 and Donor #5 that scored positive for KLH- and PA-driven proliferation were cultured for 24 h in medium without IL-2. Cells were then stimulated with autologous monocytes in the presence or absence of KLH or PA. After 5 d, cells were harvested and stained for expression of CD25 and ICOS. Shown is the percentage of CD25⁺ ICOS⁺ T cells in cultures in the absence or presence of antigen. (B) CD25⁺ ICOS⁺ T cells were sorted and cloned by limiting dilution. Shown is the percentage of KLH- or PA-specific T cell clones among the growing clones isolated from each culture. Two representative experiments of six performed.