Inflammatory cell recruitment to local sites of tissue injury and/or infection is controlled by many signaling processes influencing cell-to-cell interactions between vascular endothelial cells (EC) in post-capillary venules and circulating leukocytes. Here we report that the ATP-release channel Pannexin1 (Panx1) opens downstream of EC activation by tumor necrosis factor α (TNF α). This process involves activation of Type 1 TNF receptors, recruitment of Src Family Kinases (SFK), and SFK-dependent phosphorylation of Panx1. We report a previously unidentified role for Panx1 channels in promoting leukocyte adhesion and emigration through the venous wall during acute systemic inflammation. The present application further discloses that Panx IL2 peptide consisting of amino acid sequence KYPIVEQYLKYGRKKQRR (SEQ ID NO: 3) or 10Panx1 peptide consisting of amino acid sequence RQAAFVDSY (SEQ ID NO: 8) are inhibitors of leukocyte adhesion.