Specific recognition of original stimulator leukemic cells by the CD4⁺ T-cell clone 6.2. (A) The proliferative activity of different types of T-cell clones against patient's leukemic cells (AML cells), patient's EBV-BLCL, and HLA matched PBMCs. For each type of clone, the reactivity of one representative clone is shown. The number of clones displaying similar reactivity patterns is indicated in the brackets. (B) The proliferative activity of T-cell clone 6.2 against leukemic cells, patient's monocytes, patient's transformed or untransformed B cells, and unrelated PBMC that share HLA class II antigens with the AML patient. CD14⁺ monocytes and CD19/20⁺ B cells were isolated from PBMC of the patient by FACS sorting. Similar results were obtained in at least three independent experiments.