Lymphocytes are extremely important in the body's defense against various
infections. The two major types of lymphocytes are T cells that are involved
in cell-mediated immunity and the B cells that are involved in antibody
production. Lymphocytes are usually elevated in viral infections. Low
lymphocyte numbers may be seen in different diseases such as hepatitis,
lymphoma, or AIDS. The normal range of the lymphocyte count is 900 -
4500/µL. Monocytes are commonly known as macrophages and function in the
phagocytosis of organisms and other invading organisms. They are elevated in
blood diseases, certain infections or autoimmune diseases. The normal range
for the monocyte count is 90-1000 /µL.
Bacterial infections will often cause an increase in the total WBC count. If
this count is elevated (called leukocytosis), it may indicate the presence
of infection. Neutrophils normally consists of band neutrophils and
segmented neutrophils. Band neutrophils are less mature cells where the
nucleus has not yet segmented. They normally make up 0-6% of the WBCs.
Segmented neutrophils are the most mature type of cells. In some infectious
conditions, immature band cells increase in the blood creating a situation
called a "left shift." Individuals with chronic allergic conditions (such as
atopic rhinitis or extrinsic asthma) usually have elevated circulating
eosinophil counts.
