Modulation of Th1/Tc1 cell IL-2 secretion with adenosine A_2A receptor agonists and antagonists: dose-response relationship. Th1/Tc1 cells (0.5 × 10⁶/mL) were restimulated on day 5 of culture with 3/28 beads alone (control) or with A₁ receptor agonist (CPA), A_2A receptor agonist (CGS21680), A_2A and A_2B receptor agonist (NECA), and A₃ receptor agonist (Cl-IB-MECA) at the concentrations indicated (A). After 24 hours, resultant supernatants were evaluated for IL-2 content by ELISA, with values expressed as a percentage of control IL-2 secretion. In additional conditions, day 5 restimulation was performed in the presence of both CGS (10^-7 M) and the adenosine A_2A receptor antagonists ZM241 385 or SCH58 261 at the concentrations indicated (B).