CD4 and melanoma: The data supported prolonged long-term survival of patients treated with a vaccine comprised of 12 class I MHC-restricted peptides designed to induce CD8+ T cell responses (12MP) plus 6 class II MHC-restricted peptides designed to induce CD4+ T cell responses to melanoma antigens (6MHP), compared to vaccination with 12MP plus a tetanus toxoid peptide for activation of CD4+ T cells that were not melanoma-cognate.