T-cell clone 6.2 is restricted by HLA-DRB3 locus product HLA-Dw26 and specifically recognizes HLA-Dw26–positive leukemic cells. (A) Effect of HLA specific MoAbs on the recognition of leukemic cells by T-cell clone 6.2 (left panel) and a control DP reactive T-cell clone (right panel). The target specificities of the MoAbs are indicated in brackets. MoAbs were added in the proliferation assays at 1:100 dilution. ND, not tested. (B) Proliferative activity of T-cell clone 6.2 (left panel) and the HLA-Dw26 specific alloreactive T-cell clone (right panel) against different leukemic and nonleukemic cells. Patients no. 2 and 3 are HLA-Dw26–positive AML-M1 patients; patients no.4 to 10 are HLA-Dw26–negative AML or ALL patients (3 AML-M1, 1 AML-M3, 1 AML-M5, 1 ALL patient). MoAb 17.3.19.1 is added in the assay. CD14⁺ monocytes from patient no. 2 were obtained from PBMC by FACS sorting. EBV-BLCL and PHA blasts were also tested after culturing with GM-CSF (800 U/mL) + TNF-α (50 U/mL) + IL-4 (500 U/mL) for 72 hours. The thymidine uptake of T-cell clone 6.2 alone and the stimulator cells alone did not exceed 500 cpm.