Monocytes are pivotal in the innate immune response and progression of chronic inflammatory and degenerative disease. The recruitment of monocytes driven by chemical mediators is essential for host defence but also contributes to monocyte involvement in disease pathogenesis. C-C chemokine (C-C motif) CCL2 is a chemoattractant that acts through G-protein coupled receptors (GPCRs) to produce changes in cytosolic calcium levels that drive monocyte function. Similarly, Adenosine-5′-Triphosphate (ATP) is a signalling molecule that acts through GPCRs and is released by dying cells as a “come find me” signal for leukocytes. Exploring the signalling pathways of these molecules and how they interrelate may therefore aid in identifying the chemical imbalances involved in disease. Studies were performed with human THP-1 cells (acute monocyte leukaemia) or peripheral blood mononuclear cells (PBMCs). All calcium (Ca2+) mobilisation studies were performed with FLUO-4-AM with or without (w/o) Ca2+(1.5mM). Initial studies explored the effect of apyrase, an ATP/ADP scavenger. THP-1s and PBMCs were pre-incubated for 10min with or w/o apyrase (2U/mL) and were stimulated with CCL2 (1-500ng/mL). The effect of apyrase on THP-1 chemotaxis was also studied using a transwell migration assay. To further elucidate an association between purinergic and chemokine signalling, the ecto-ATPase inhibitor ARL-67156 (100µM), P1 antagonist CGS-15943 (2.5µM), and the P2Y/P2X antagonist Suramin (100µM) were explored. ATP secretion was tested using the luciferase-luciferin assay. Hypothesis testing performed by means of paired Student t-test. Chemokine-evoked Ca2+ responses in THP-1 cells were inhibited by apyrase. The inhibitory effect of apyrase was also observed in PBMCs. In THP-1s, apyrase inhibited CCL2 (50ng/mL:Emax) responses by 60% (n=6, p<0.05) and also produced a 5-fold shift in the CCL2 EC50 response (p<0.05). THP-1 chemotaxis toward CCL2 was significantly attenuated in the presence of apyrase (n=3, p<0.05). ARL-67156 potentiated Ca2+ responses at 10 (EC20) and 20ng/mL (EC50) CCL2 (n=4-9, p<0.05). An involvement of P1 receptors was explored through CGS-15943 and showed a potentiation of CCL2 EC20 Ca2+ responses (n=4, p<0.05). P2 receptor involvement was tested with Suramin and gave a >90% inhibition of CCL2 Emax responses (n=3, p<0.05). Our data also demonstrates that Ca2+ responses to CCL2 are associated with a secretion of ATP (n=3, p<0.05). In conclusion, CCL2 evoked calcium signalling in human leukocytes is facilitated by a concomitant release of ATP acting through purinergic receptors. Ecto-ATPases and adenosine P1 receptors also act to modulate this process. Our data suggests that purinergic receptors offer a new route for therapeutic intervention of C-C chemokine mediated diseases.