These different functions are performed by blood cells and the liquid part of the blood, called plasma. There are three main types of white blood cells. These and the second type, the monocytes, respond to many different types of infection and also defend by engulfing foreign substances. The third type of white blood cells, known as lymphocytes, react to specific infecting agents. The lymphocytes include B cells and T cells.
B cells produce antibodies, and T cells attack foreign and virus-infected cells.
They stop loss of blood from the bloodstream by forming plugs in vessel holes. When any of your blood vessels is damaged, platelets gather to plug the site of injury. The plasma, a yellowish liquid, carries other proteins as well as the clotting factors. Plasma can be defined as what is left after the cells are removed from your blood. Serum is plasma from which the clotting factors also have been removed.