Blood carry oxygen, instead of hemoglobin. Insects and some mollusks use a fluid called hemolymph instead of blood, the difference being that hemolymph is not contained in a closed circulatory system. In most insects, this "blood" does not contain oxygen-carrying molecules such as hemoglobin because their bodies are small enough for their tracheal system to suffice for supplying oxygen. Jawed vertebrates have an adaptive immune system, based largely on white blood cells. White blood cells help to resist infections and parasites. Platelets are important in the clotting of blood. Arthropods, using hemolymph, have hemocytes as part of their immune system. Blood
Blood doping or storage is another issue. Contamination was seen in 1 in every 500,000 transfusions of red blood cells in 2002. Blood contamination can lead to septicemia or an infection that affects the whole body. Certain medications used to increase red blood cells can reduce liver function and lead to liver failure, pituitary problems, and increases in cholesterol levels. Blood doping Blood doping is the practice of boosting the number of red blood cells in the bloodstream in order to enhance athletic performance. Because such blood cells carry oxygen from the lungs to the muscles, a higher concentration in the blood