Figure 1.

γδ T cells, predominantly Vδ1⁺ T cells, are rich in tissues such as colon and skin, where they interact with tissue-selecting proteins of the BTNL family. High expression of NCRs (e.g. NKG2D, NKp30, DNAM-1) allows these cells to respond to stress ligands [MICA/B, ULBPs] in an MHC-unrestricted and non-clonal fashion, and at the same time to recognize TCR-specific ligands. Activation of γδ T cells involves direct cytolysis of target cells as well as the production and release of cytolytic granules, chemokines and T_H1 cytokines. Bridging the innate and adaptive systems, γδ T cells have been shown to attract and activate antigen-presenting cells (APCs), αβ T cells and B cells, thereby orchestrating adaptive immune responses. In blood, mostly Vδ2Vγ9 T cells survey for metabolically hyperactive cells, sensing intermediates of the mevalonate pathway through interactions with BTN3A1.