Preparation of Peripheral Blood Mononuclear Cells (PBMCs) for subsequent EPC quantification PBMCs will be collected using standard techniques. In brief PBMCs will be isolated from venous blood collected into a 9.7ml sodium heparin blood tube (which will subsequently be stored at room temperature for up to 4 hours). The blood samples will then be centrifuged (1500g for 10 min at 4⁰C) and the plasma layer will be collected for later biomarker analysis (aliquots of plasma will be frozen at -80⁰C until use). The buffy coat layer (the white opaque layer that lies directly above the red cell pellet) will be used for PBMC isolation. To isolate the PBMCs, the buffy coat will be centrifuged at 400g on a Ficoll gradient (1.077g/ml) for 30 minutes and the resulting cellular layer will then undergo 3 further washes (300g for 10 minutes and 20g for 10 minutes X2) to wash the cells and deplete platelets. To calculate the number of PBMC isolated, the pellet will be suspended in a known volume of Phosphate Buffered Solution (PBS) (1ml) and a small quantity (10µl) will be assessed for quantity and viability under an inverted microscope using a haemocytometer and a vital stain (Trypan blue).