Platelets and soluble CD154 as central linkers of rheumatoid arthritis and atherosclerosis. Platelets and platelet microparticles (PMPs) have been shown to contribute to both rheumatoid arthritis (RA) and atherosclerotic development. The vast majority of soluble CD154 (sCD154) found in circulation originates from activated platelets and this platelet inflammatory mediator may represent the biological link between both complications. Enhanced levels of sCD154 correlate with RA disease severity, as well as acute coronary syndromes (ACS). Moreover, a positive feedback loop between RA activity and sCD154 and platelets may take place, whereby disease initiation and progression can reciprocally exacerbate platelet activation and sCD154 levels, leading to atherosclerotic development and vascular complications. As common denominators to both complications, platelets and their release of sCD154 may represent pivotal contributors to atherogenesis initiation in RA patients.