Gamma-Delta T Cells: Unseen Immune Warriors

Our bodies need protection against pathogen invasion and for that we employ our immune system which is armed with an arsenal of cells and proteins. This immune network is destined to eliminate microbes and substances determined to pose significant threat to the normal functioning of our bodies by confronting viruses, bacteria, toxins, fungi and parasites, or even by battling tumoral cells. So, the immune system develops mechanisms at least equal in effectiveness and ingenuity to the infectious or transforming threat. At the same time, the maintenance of homeostasis and prevention of self-destruction is a very important function managed also by the immune system via tolerance mechanisms. This orchestration and customisation of the immune system aim in securing our best survival1,2. The network of immune cells is usually divided into the innate and adaptive leg (figure I.1). The first harbours ready-for-action cells (e.g. monocytes, neutrophils, natural killer cells) and the second highly specialised agents (T and B lymphocytes). Even though separated in categories the cross talks and cooperation between the two legs are constant and crucial. T and B lymphocytes recognise and bind a broad range of antigens through the highly diverse antigen receptors on their surface (T-cell receptor for T lymphocytes and B-cell receptor for B lymphocytes) and confer the essential aspect of immunological memory1. In the T spectrum, there are unconventional cases of more rapid responders such as mucosal-associated invariant T (MAIT) cells (αβ), natural killer T (NKT) cells (αβ) or the γδ T cells3. The focus of this work is on the human γδ T cells and especially the Vγ9Vδ2 T cell population which provide unique functional specialisation.