Abstract
Whether γδ T cells inhibit or enhance the Foxp3 T cell response depends upon their activation status. The critical enhancing effector in the supernatant is adenosine. Activated γδ T cells express adenosine receptors at high levels, which enables them to deprive Foxp3+ T cells of adenosine, and to inhibit their expansion. Meanwhile, cell-free supernatants of γδ T cell cultures enhance Foxp3 T cell expansion. Thus, inhibition and enhancement by γδ T cells of Foxp3 T cell response are a reflection of the balance between adenosine production and absorption by γδ T cells. Non-activated γδ T cells produce adenosine but bind little, and thus enhance the Foxp3 T cell response. Activated γδ T cells express high density of adenosine receptors and have a greatly increased ability to bind adenosine. Extracellular adenosine metabolism and expression of adenosine receptor A2ARs by γδ T cells played a major role in the outcome of γδ and Foxp3 T cell interactions. A better understanding of the functional conversion of γδ T cells could lead to γδ T cell-targeted immunotherapies for related diseases.
Highlights
Recent studies from several laboratories [1,2,3,4,5], including ours [6,7,8,9], have demonstrated that γδ T cells have a significant regulatory effect on autoimmune diseases [6,7,8,9]
We propose that a better understanding of the activation-dependent, adenosine-related functional conversion of γδ T cells could lead to γδ T cell-targeted immunotherapies in autoimmunity and other conditions affected by Foxp3+ regulatory T cells
In a 24-well plate, 1 x 106/well T cell receptor (TCR)-δ-/- responder T cells were cultured in IL-2-containing medium in the absence or presence of activated γδ T cells (2%, right panel) or γδ T cell supernatant (1:5 vol:vol, middle panel)
Summary
Recent studies from several laboratories [1,2,3,4,5], including ours [6,7,8,9], have demonstrated that γδ T cells have a significant regulatory effect on autoimmune diseases [6,7,8,9]. Our recent studies demonstrated that activated γδ T cells have an increased enhancing effect on the autoimmune response [7,14]; that the regulation of immune responses by γδ T cells and ATP/adenosine metabolism are intimately connected [15,16,17,18]; that competitive binding of adenosine among immune cells plays a key role in the outcome [15,18]. Activated γδ T cells had an increased expression of high-affinity adenosine receptors (A2ARs) and decreased expression of CD73, which converts ATP/AMP into adenosine [19,20]. Whether such changes accounted for functional conversion had not been determined. We show that activated γδ T cells have an inhibitory effect on the Foxp T cell
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