Update on T-cell immunity: Implications for tumor immunology

The association between the immune system and malignancy is at the forefront of research aimed at identifying and developing effective immunotherapies to treat and suppress cancer. Understanding the mechanisms underlying the biology, differentiation and effector functions of key immune cells in the tumor microenvironment is central to this process. The stimulation of T cells results in their activation, triggering the release of cellular mediators, including cytokines and chemokines. The interplay between these components determines the polarization of T cells into phenotypically-, functionally- and transcriptionally-distinct subsets (e.g. T-helper [Th] 1, Th2, Th17 and T-regulatory cells). Given that antigen recognition, costimulation and the cytokine milieu are critical signals in T-cell activation and differentiation, they represent potential and important therapeutic targets for modulating immune responses in disease. The aim of this article is to review the role of T cells in immune protection and pathogenesis, and to discuss the key pathways involved in these processes.