The T cells activate and help other cells destroy viruses and other foreign material. There are other situations that bring about reduced lymphocyte numbers but they are fairly uncommon. An increase in the number of lymphocytes does not happen as consistently as might be expected but is noted in prolonged illnesses. Examples of this would be when bacterial or viral infections have gone on for a long time or in certain autoimmune diseases. A common cause of increased lymphocytes is leukemia which is a cancer of blood cell production that is usually fatal.
Monocytes develop and are stored in the spleen and bone marrow.
They also have the ability to eat or engulf foreign material such as infectious organisms. Additionally they secrete various protein molecules that help in the clean up of inflamed and irritated tissue. Their numbers do not very greatly unless there is a cancerous leukemia condition affecting their cell lines. Platelets The final component that we study when interpreting the CBC, are the platelets. They serve a vital function in the formation of clots.