The macrophage adenosine 5’ triphosphate (ATP)-gated P2X₇ receptor (P2X₇R) couples to opening of a cation permeable channel, triggers permeation of large dyes into the cell (<900 Da), rapid externalization of phosphatidylserine (PS) and secretion of pro-inflammatory cytokines. All these events can occur in the absence of cell lysis (Moore & MacKenzie, 2006; MacKenzie et al, 2001). Changes in lipid topology are reported to play a crucial role in de-encyrption of tissue factor (TF); a membrane bound glycoprotein that initiates the extrinsic clotting cascade (Price et al; 2004; Wolberg et al; 1999). We have investigated whether macrophage P2X₇Rs can interact with pro-thrombotic signalling pathways and de-encrypt cell surface TF. In the current study we have evaluated the ability of P2X₇Rs to de-encrypt cell surface TF in RAW246.7 macrophages. Active TF complexes with the activated protease, Factor VII (FVIIa), and processes Factor X (FX) into active FX (FXa) (Price et al; 2004). De-encryption of TF was monitored in the presence of FX (150 nM) and FVII (5 nM) where generation of FXa was detected using a chromogenic FXa substrate (0.5 mM S-2765^TM). All experiments were conducted at time points where no release of lactate dehydrogenase could be detected (Moore & MacKenzie, 2006). Assays were performed at 37 ^oC in NaCl-based saline containing (in mM) 147 NaCl, 2 KCl, 10 HEPES, 12 Glucose, 1 MgCl₂, 2 CaCl₂ (pH 7.3 with NaOH). Data expressed as mean ± s.e.m. RAW 264.7 macrophages were pulsed with 3 mM ATP for 5 mins and an increase in FXa was detected above background levels (ΔFXa = 249 ± 42 pM, n = 3, p<0.01 versus control using one-way ANOVA with Dunnetts Post-Hoc Test). Pre-incubation of cells with the P2X₇R antagonist KN-62 (10 μM, 5 min) abolished this increase (n = 3, p>0.05 versus control using Students T-test). ATP-induced increases in FXa generation was found to be both PS and TF dependent as incubation of stimulated cells with either 500 nM Annexin-V or 25 μg ml^-1 TF IgG abolished increases in FXa generation (n = 3, p>0.05 versus control using Students T-test). Increases in FXa generation were not accounted for by an increase in surface expression of tissue factor. FACS analysis using TF IgG, demonstrated that brief 5 min ATP stimulation (3 mM) gave no significant change in percentage of cells expressing TF (n = 3, P>0.05) and furthermore led to a reduction in mean fluorescence intensity (n = 3, p<0.01). These results suggest that macrophage P2X₇Rs, classically described as pro-inflammatory receptors, can also engage pro-thrombotic signalling pathways with rapid de-encryption of cell surface TF.