CD4 and neoplasm: Again, wild type melanoma cell lines expressing MHC class II molecules or tumor cells transfected with plasmid encoding SSX2 were not recognized by epitope-specific CD4+ T cells directly, however, p37–51 peptide-pulsed tumor cells were recognized by both SSX2 p37–51-specific CD4+ T cells and SSX2 p41–49 peptide-specific CD8+ T cells.