Antigen
Also, an antigen is a molecule that binds to Ag-specific receptors, but cannot necessarily induce an immune response in the body by itself. Antigens are usually proteins, peptides (amino acid chains) and polysaccharides (chains of monosaccharides/simple sugars) but lipids and nucleic acids become antigens only when combined with proteins and polysaccharides. In general, saccharides and lipids (as opposed to peptides) qualify as antigens but not as immunogens since they cannot elicit an immune response on their own. Furthermore, for a peptide to induce an immune response (activation of T-cells by antigen-presenting cells) it must be a large enough size, since peptides too small will also not elicit an immune response.
Adoptive cell transfer
Cancer-testis antigens are a family of intracellular proteins that are expressed during fetal development, but with little expression in normal adult tissues. More than 100 such molecules are epigenetically up-regulated in from 10 to 80% of cancer types. However, they lack high levels of protein expression. Approximately 10% of common cancers appear to express enough protein to be of interest for antitumor T cells. Low levels of some cancer-testes antigens are expressed in normal tissues, with associated toxicities. The NYESO-1 cancer-testes antigen has been targeted via a human TCR transduced into autologous cells. ORs were seen in 5 of 11 patients with metastatic melanoma and 4 of 6 patients with highly refractory synovial cell sarcoma.