In this study, the investigators will determine whether patients with documented atherosclerosis are characterized by specific epigenetic changes in circulating cells of the innate immune system, compared to patients without atherosclerosis.

Rationale: The innate immune system plays a pivotal role in the development and progression of atherosclerosis. Recently, it was reported that monocytes can develop a long-lasting immunological memory after stimulation with various microorganisms, which has been termed 'trained innate immunity'. This memory is induced by epigenetic reprogramming. We hypothesize that trained monocytes augment atherogenesis.

Objective: The main objective is to study whether patients with coronary atherosclerosis show specific epigenetic changes in the promoter regions of pro-inflammatory cytokines and chemokines and whether this correlates with the inflammatory phenotype of these cells.

Study design: Observational study

Study population: Adult patients who have had computed tomography coronary angiography because of chest pain: 20 patients without atherosclerosis and 20 patients with severe atherosclerosis will be included.

Inclusion Criteria:

• Patients (male/female),
• aged >18 years,
• admitted to the acute coronary unit of the CWZ hospital for evaluation of chest pain.
• No coronary atherosclerosis
• Or Severe atherosclerosis

Exclusion Criteria:

• Signs or symptoms of a current infection (fever, chills)
• Auto-immune diseases (such as rheumatoid arthritis)

Adult patients >18 years who have underwent CCTa scanning beacuse of chest pain.