Comprehensive Phenotyping of T Cells Using Flow Cytometry.

The T cell compartment can form a powerful defense against extrinsic (e.g., pathogens) and intrinsic danger (e.g., malignant cells). At the same time, specific subsets of T cells control this process to keep the immune system in check and prevent autoimmunity. A wide variety in T cell functionalities exists, which is dependent on the differentiation and maturation state of the T cells. In this review, we report an overview for the identification of CD4+ T-αβ cells (T-helper (Th)1, Th2, Th9, Th17, Th22, and CD4+ regulatory T cells), CD8+ T-αβ cells (cytotoxic T lymphocyte (Tc)1, Tc2, Tc9, Tc17, and CD8+ regulatory T cells), and their additional effector memory status (naïve, stem cell memory, central memory, effector memory, and effector) using flow cytometry. These different subsets can be discriminated based on selective extracellular markers, in combination with intracellular transcription factor and/or cytokine stainings. Additionally, identification of very small subsets, including antigen-specific T cells, and important technical considerations of flow cytometry are discussed. Together, this overview can be used for comprehensive phenotyping of a T cell subset of interest.