<P> Neoantigens are those that are entirely absent from the normal human genome . As compared with nonmutated self - antigens, neoantigens are of relevance to tumor control, as the quality of the T cell pool that is available for these antigens is not affected by central T cell tolerance . Technology to systematically analyze T cell reactivity against neoantigens became available only recently . </P> <P> For virus - associated tumors, such as cervical cancer and a subset of head and neck cancers, epitopes derived from viral open reading frames contribute to the pool of neoantigens . </P> <P> Tumor antigens are those antigens that are presented by MHC class I or MHC class II molecules on the surface of tumor cells . Antigens found only on such cells are called tumor - specific antigens (TSAs) and generally result from a tumor - specific mutation . More common are antigens that are presented by tumor cells and normal cells, called tumor - associated antigens (TAAs). Cytotoxic T lymphocytes that recognize these antigens may be able to destroy tumor cells . </P> <P> Tumor antigens can appear on the surface of the tumor in the form of, for example, a mutated receptor, in which case they are recognized by B cells . </P>

When is a protein on a blood cell considered an antigen