Subtype-specific dissection of the HLA-DR restriction of the p635-649 induced T-cell response. Using allogeneic LCLs (3 × 104/well) with different HLA-DR subtypes as APCs for cells (500/well) of the p635-649–specific CD4%⁺ T-cell clone 60 allowed determining the HLA-DR subtype-specific restriction of the anti–p635-649 reaction. The HLA-DR set-up of the 3 LCLs derived from Co90, Co7, and MGAR, respectively (Table 3), identified HLA-DRB1*1401 as the restricting subtype because in the allogeneic setting only LCLs from Co 90 induced significant IFN-γ production (P < .01) in response to the HOM-TES-14/SCP1–derived epitope p635-649 in T cells from clone 60.