Gamma delta T-cells

Published on July 10, 2022   27 min

Other Talks in the Series: The Immune System - Key Concepts and Questions

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Hello. My name is Bruno Silva-Santos. I'm a Professor of Immunology at the Medical School of the University of Lisbon in Portugal. I'll be lecturing on γδ T cells.
Until the mid-1980s, lymphocytes were thought to be either B cells or T cells, and in this case, αβ T cells, meaning cells expressing a T cell receptor composed of an α and a β chain. But in 1984, γδ T cells joined this lymphocyte family and were characterised as expressing a different antigen receptor. This antigen receptor was composed of a γ and a δ chain and was shown to bind very different ligands compared to their αβ T cell counterparts.
Actually, γδ T cells were shown to be conserved throughout evolution, ever since the emergence of jawed vertebrates 450 million years ago, essentially with the shark. Throughout evolution, all the other organisms that you can see in this picture actually contain γδ T cells besides αβ and B cells. This trio of lymphocytes has been conserved throughout evolution.
γδ T cells are defined by the expression of the TCRγ and TCRδ chain that paired together to constitute the γδ T cell receptor. This is something that around 1-2% of T cells do, both in mice and humans. As you can see in the human blood FACS plot, we have around 2% of leukocytes expressing this γδ t cell receptor. This is in the human blood, it can be very different in some mucosal surfaces, like the intestine, where γδ T cells can account for up to 30% of the lymphocytes that live in those surfaces. They are expressed by γδ T cell receptor and what's very peculiar about this γδ T cell receptor, is that it does not respect the rule of the conventional T cell receptor of binding the MHC presenting molecule.