Hitting the brake: miR-31 regulates CD8 T cell effector function

Cytotoxic CD8 T cells have pivotal effector and regulatory immune-functions and are, as such, involved in the host-immune response following infection. Dysfunction of CD8 T cells, on the other hand, may contribute to autoimmunity. CD8 T cells exert their function by releasing cytotoxic mediators and cytokines. Acute infection triggers a response to effectively clear the pathogen and develop long-lasting protective memory, while chronic infections may lead to exhaustion and dysfunction of CD8 T cells. The latter phenomenon relates to the tunable balance of the immune system to preserve tolerance and prevent development of autoimmunity. CD8 T cells also play a crucial role in preventing development of cancer cells. Tumor cells may evade an effective anti-tumor immune response and clinical exploitation of immune checkpoints to break this tolerance and induce anti-tumor immunity clearly illustrates the two-edged characteristics of the immune response. Vice versa, autoimmune disorders and chronic infections may lead to the onset of cancer, which suggests that these pathological conditions may share mutual pathways. Understanding the molecular basis of autoreactive and defective CD8 T cell responses provides a basis for the rational design of immunotherapies aiming to restore CD8 T cell function and combat chronic viral infections and cancer.