Chemotactic effects of adenosine. (A) Semiquantitative RT-PCR revealed the expression of A1, A2a, A2b, and A3 receptors on human neutrophils, monocytes, and lymphocytes. (B) Adenosine (from left, 0, 0.1, 1, 10, 100, 1000 μM) and CPA (from left, 0, 0.01, 0.1, 1, 10, 100 μM), but not CGS21680 (from left, 0, 0.1, 1, 10, 100, 1000 μM) induced chemotaxis by human monocytes. (^*P < .05). (C) Adenosine and its analogs did not induce a transient Ca²⁺ influx. ATP and RANTES/CCL5 induced robust Ca²⁺ influx.