CD8⁺ T cell-based immunotherapy: Promising frontier in human diseases

The abundant cell components of the adaptive immune system called T lymphocytes (T cells) play important roles in mediating immune responses to eliminate the invaders and create the memory of the germs to form a new immunity for the next encounter. Among them, cytotoxic T cells expressing cell-surface CD8 are the most critical effector cells that directly eradicate the target infected cells by recognizing antigens presented by major histocompatibility complex class I molecules to protect our body from pathological threats. In the continuous evolution of immunotherapy, various CD8⁺ T cell-based therapeutic strategies have been developed based on the role and molecular concept of CD8⁺ T cells. The emergence of such remarkable therapies provides promising hope for multiple human disease treatments such as autoimmunity, infectious disease, cancer, and other non-infectious diseases. In this review, we aim to discuss the current knowledge on the utilization of CD8⁺ T cell-based immunotherapy for the treatment of various diseases, the molecular basis involved, and its limitations. Additionally, we summarize the recent advances in the use of CD8⁺ T cell-based immunotherapy and provide a comprehensive overview of CD8⁺ T cells, including their structure, underlying mechanism of function, and markers associated with CD8⁺ T cell exhaustion. Building upon these foundations, we delineate the advancement of CD8⁺ T cell-based immunotherapies with fundamental operating principles followed by research studies, and challenges, as well as illustrate human diseases involved in this development.