Venous EDTA blood (10ml) on each occacasion will be drawn from each case one hour prior to surgery, 1 hour and 3 hours post surgery. Then they will be asked to return to the hospital 3 to 5 days post surgery for one more blood taking, and macrophages will be separated from the blood and total RNA will be extracted as soon as possible after blood taking from half the total cells. The remainder of the cells (macrophages) will be stored at -80oC and batched for DNA extraction. Venous EDTA blood (20ml) will be drawn from each control subject at a time convenient to them and again, 3 to 5 days post first blood taking. The blood taken from the control subjects will be treated in exactly the same way as with blood taken from the case subjects. Therefore, four samples in total will be obtained from each case and control subject.