Red blood cell endothelial cells. Exposure of red blood cells to physiological levels of shear stress activates nitric oxide synthase and export of nitric oxide, which may contribute to the regulation of vascular tonus. Red blood cells can also produce hydrogen sulfide, a signalling gas that acts to relax vessel walls. It is believed that the cardioprotective effects of garlic are due to red blood cells converting its sulfur compounds into hydrogen sulfide. Red blood cells also play a part in the body's immune response: when lysed by pathogens such as bacteria, their hemoglobin releases free radicals, which break down the pathogen's cell
Blood donation in England and each donation usually gives two or three adult doses. One adult dose of platelets would otherwise require four whole blood donations. Blood is made in the bone marrow. It is composed of red blood cells, platelets, plasma and white blood cells, collectively referred to as blood components. Donations given at regular blood donation sessions are referred to as "Whole Blood". Platelets are very small cells. They work with the clotting factors in plasma to form a mesh "plug" to stop or prevent bleeding. Plasma is the fluid part of the blood. It contains protein, salts and clotting factors. White