γδT-cells are a subset of T-cells which express a γδTCR. They are very similar to αβT-cells, but they are less well defined and may have unknown roles in the immune system.
All jawed vertebrates from shark to human have γδT-cells. Conservation of γδT-cells throughout almost 500 million years of evolution is further testament to their importance. Indeed, phylogenetic analysis of antigen receptor constant domains suggests that the γδTCR predates the B-cell receptor (antibody) and αβTCR. Thus γδT-cells may be the cells that taught the immune system to remember. If indeed γδT-cells did educate the adaptive immune system then we might expect that they could perform the roles of their evolutionary cellular descendents that form the cornerstones of antibody and αβT-cell immunity. In support of this notion, Bernhard Moser and Matthias Eberl in the department are finding that human γδT-cells possess a high degree of functional plasticity. Professor Moser's laboratory published a recent report in Science that shows that peripheral blood γδT-cells that bear a receptor made from the Vγ9 and Vδ2 genes can be extremely effective at presenting antigen to their αβTCR expressing evolutionary descendents. We are also finding that different subsets of γδT-cells can perform other important immune functions that until now have been assumed to be exclusive roles of other immune cells.
γδT-cells form an important arm of adaptive immunity and that they can perform many different roles. A full understanding of these roles awaits the discovery of the ligands recognized by γδTCRs. Our Department has manufactured and biophysically characterized more human αβTCRs than the rest of the world combined. We are now applying our skills to the manufacture of soluble γδTCRs with a view to discovering the ligands for this forgotten arm of adaptive immunity.