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 ( beta) natural killer T (NKT) cells ( beta) or the Gammad T cells3. The focus of this
work is on the human Gammad T cells and especially the VGamma9Vd2 T cell population which
provide unique functional specialisation.
