Endogenous adenosine is required to prevent death by autoimmunity. (A) In vivo A_2AR mRNA expression as determined by Affymetrix microarray analysis for 6.5⁺ TCR transgenic clonotypic T cells specific for hemagglutinin (HA) that had been transferred into B10.D2 mice (NT), vaccinated B10.D2 mice (Vac), or C3HA mice (C3HA). (B) Survival curve of C3HA mice given Wt () or A_2AR^−/− 6.5⁺ T cells (○) (n = 5 each condition). Data are representative of 2 independent experiments.