Unlke the digestive or circulatory systems, the immune system is not contained within a set of organs or network of vessels… It’s elements permeate nearly every part of the body.
Imagine the components of this immune system glowing fromwithin. It’s key operators, a class of white blood cells known as lymphocytes, appear from head to toe. Like minute, twinkling lights, a trillion or more lymphocytes illuminate the blood, lungs, liver, stomach and nearly every other body tissue. So do scavenging white blood cells called phagocytes (from greek, phagein: to eat).
Amazing isn’t it?