Fig. 1.

Adenosine synthesis and control of host responses to limit tissue damage. ATP can accumulate in areas of inflammation or hypoxia from dead cells or bacteria [2]. The metabolism of ATP can be achieved by CD39 and CD73 leading to the accumulation of adenosine (ADO). These enzymes are expressed differentially by various cells but both are found on Treg and contribute to their regulatory function. Subsequently, the adenosine can interact with any of the four receptor subtypes, primarily the A_2A and A_2BAR but possibly A1AR and A3AR as well. The short half-life of adenosine requires a close juxtaposition among cells producing and responding to its signals suggesting its effects are largely paracrine or autocrine. This figure is modified from [26]