Researchers investigating potential cures for cancer cells face the numerous problems which our immune system faces when trying to clear out cancerous cells. Namely, cancerous cells down regulate MHC class I expression and the B7 molecule which are both needed for activation of T lymphocytes. In addition, researchers have long since been trying to isolate antigens which are specific to cancerous cells which the immune system uses to differentiate cancerous cells from normal cells. These antigens are currently being tested in numerous types of vaccine development.
Two types of antigens have been identified on tumor cells: Tumor-specific transplantation antigens (TSTAs) which are unique to cancer cells, and tumor-associated transplantation antigens (TATAs) which are found on both cancer and normal cells. However TATAs may be expressed at increased levels on cancer cells compared to normal cells and thus have been able to play a role in inducing immune responses. Peptides encoded by oncogenes can also serve as tumor markers and are being assessed in their ability to induce an immune response.
Ideal cancer vaccines need to induce a strong T cell response as well as a humoral response. Cyto-toxic T lymphocytes (CTLs) appear to play key roles in the immunological destruction of many cancer cells. However T-helper cells are needed for the activation of tumor-destructive macrophages, NK cells and lymphokine-activated killer (LAK) cells. This section will address the following key areas currently being explored in the development of cancer vaccines:
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