Demonstration of the HLA-DR restriction of the CD4⁺-mediated T-cell response against the HOM-TES-14/SCP1–derived peptide p635-649. The HLA-DR restriction of the anti–p635-649 T-cell response (1.5 × 104 CD4⁺ T cells/well) was demonstrated by ELISPOT assay by significant (P < .01) blocking of the response by incubating the APCs with anti-DR antibody (clone L243) after p635-649 stimulation for 28 days. Treatment of p635-649–pulsed autologous PBMCs (5 × 104/well) with anti-DP antibody had no effect. Similarly, the reaction was significantly (P < .01) blocked after incubation of the effector cells with anti-CD4 antibody (clone MT310).