CD4 T Cells in Antitumor Immunity

T lymphocytes expressing the CD4 marker have diverse functions within the immune system. A subset of CD4 T lymphocytes known as T-helper (Th) cells is essential in the generation and augmentation of humoral immune responses and cell-mediated immunity. Other subsets of CD4 T cells known as T regulatory cells have an opposite function and will be described in a different article. Here we review the important role of CD4 Th cells in antitumor immunity in providing help for the generation of antibodies and CD8 cytotoxic T-lymphocytes capable of limiting tumor cell growth. Furthermore, CD4 Th cells are essential for generating memory CD8 T cells, which are responsible for preventing tumor recurrences. In addition to their intrinsic helper function, some tumor-reactive CD4 Th cells can also serve as effector cells promoting tumor eradication via production of cytostatic cytokines within the tumor microenvironment or through cell-mediated cytotoxicity. Due to their important role in antitumor responses, effective immunotherapy approaches such as antitumor vaccines include strategies to generate tumor-reactive CD4 Th cell responses.