Natural processing and presentation of the HOM-TES-14/SCP1–derived peptide p635-649. To provide evidence for the natural processing of SCP1-derived peptide p635-649, a fragment was synthesized spanning the residues p630 to p817 and including p635-649. Generating DCs in medium with increasing concentrations of p630-687 induced a concentration-dependent T-cell response of clone 60 cells (1000 cells/well), which could be blocked by anti–HLA-DR. Full-length SSX2 antigen was used as a control (P < .001). Additional pulsing of the DCs with peptide p635-649 boosted the T-cell reaction significantly (P = .05), causing an increase of spot numbers by approximately 35%.