cancers Review CD4+ T Cells: Multitasking Cells in the Duty of Cancer Immunotherapy Jennifer R. Richardson 1 , Anna Schöllhorn 1,2 ,Cécile Gouttefangeas 1,2,3,* and Juliane Schuhmacher 1,2 1 Department of Immunology, Institute for Cell Biology, University of Tübingen, 72076 Tübingen, Germany;
[email protected] (J.R.R.);
[email protected] (A.S.);
[email protected] (J.S.) 2 Cluster of Excellence iFIT (EXC2180) “Image-Guided and Functionally Instructed Tumor Therapies”, University of Tübingen, 72076 Tübingen, Germany 3 German Cancer Consortium (DKTK) and German Cancer Research Center (DKFZ) Partner Site Tübingen, 72076 Tübingen, Germany * Correspondence:
[email protected] Simple Summary: T cells bearing the co-receptor CD4 on their cell surface are a heterogeneous group of T lymphocytes that exert pro- or anti-inflammatory functions. Evidence from mouse models and cancer patients reveal that various CD4+ T cell subsets play an antagonistic role in the antitumor immune response. This review summarizes current knowledge on CD4+ T cell subsets, on how they impact tumor growth in patients, and which role these cells play in newest cancer immunotherapies. Abstract: Cancer immunotherapy activates the immune system to specifically target malignant cells. Research has often focused on CD8+ cytotoxic T cells, as those have the capacity to eliminate tumor cells after specific recognition upon TCR-MHC class I interaction. However, CD4+ T cells have gained attention in the field, as they are not only essential to promote help to CD8+ T cells, but are also able to kill tumor cells directly (via MHC-class II dependent recognition) or indirectly (e.g., via Citation: Richardson, J.R.; the activation of other immune cells like macrophages).