An observational pilot proof-of-principle study. 15 patients with significant coronary artery disease and 15 matched controls. To investigate whether long-term activation of the innate immune system, named 'trained innate immunity', occurs at the level of the bone marrow progenitor cells in patients with significant coronary artery disease and whether this correlates with the proinflammatory phenotype of monocytes.

Inclusion Criteria:

• Age ≥18 and ≤75 years
• With or without significant coronary artery disease on CCTA
• Written informed consent

Exclusion Criteria:

• Chronic infections
• Diabetes mellitus
• Medical history of any disease associated with immune deficiency
• Clinically significant infections within 3 months prior to study entry
• Recent hospital admission or surgery with general anaesthesia
• Known chronic kidney or liver disease
• Previous vaccination within 3 months prior to study entry
• Inability to personally provide written informed consent
• Inability to undergo PET-CT scanning
• Chronic use of anti-inflammatory drugs such as NSAIDs
• History of haematological malignant disease
• Documented bleeding diathesis or thrombocytopenia
• Pregnancy

This study will include 15 patients with significant coronary artery disease and 15 patients without significant coronary artery disease. Patients who have been presented to the cardiology departments of the CWZ hospital or Radboud University Medical Centre and have undergone CCTA in the past two years are eligible to participate if they meet the in- and exclusion criteria.