Health effects of tobacco the blood thicker and more likely to clot. Carbon monoxide binds to hemoglobin (the oxygen-carrying component in red blood cells), resulting in a much stabler complex than hemoglobin bound with oxygen or carbon dioxide—the result is permanent loss of blood cell functionality. Blood cells are naturally recycled after a certain period of time, allowing for the creation of new, functional red blood cells. However, if carbon monoxide exposure reaches a certain point before they can be recycled, hypoxia (and later death) occurs. All these factors make smokers more at risk of developing various forms of arteriosclerosis (hardening of the arteries).
Packed red blood cells red cells with both are called AB. Except in unusual cases like infants or seriously immunocompromised individuals, all people will have antibodies to any ABO blood type that isn't present on their own red blood cells, and will have an immediate hemolytic reaction to a unit that is not compatible with their ABO type. In addition to the A and B antigens, there are rare variations which can further complicate transfusions, such as the Bombay phenotype. The Rh blood group system consists of nearly around 50 different antigens, but the one of the greatest clinical interest is the "D" antigen,