Stephen J. Schueler, M.D.

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Weak Immune System Anatomy

To better understand immune system deficiency, it helps to understand the anatomy and composition of blood.

Blood is a circulating tissue that carries nourishment and oxygen to the cells and tissue.

Blood is composed of 3 cell types that are suspended in a protein-rich fluid called plasma:

  • Red blood cells (erythrocytes)
  • White blood cells (leukocytes)
  • Platelets (thrombocytes)

Red Blood Cells
Red blood cells contain hemoglobin, which is the molecule that carries oxygen to the tissues. A decrease in the number of red blood cells reduces the amount of oxygen that can be carried by the bloodstream. This can result in poor exercise tolerance and fatigue.

Normal ranges for the total number of red blood cells in adults are:
  • 4.6-6.2 million per cubic millimeter (males)
  • 4.2-5.4 million per cubic millimeter (females)

White Blood Cells
White blood cells are an important part of the immune system. There are several types of white cells (leukocytes) present in the blood. These cells mainly function to fight infection. Normal total ranges for white blood cells are: 4,500 - 11,000 (per cubic millimeter). Slightly higher counts are normal in children.

A white blood cell differential reports the percentages of the different types of white blood cells that comprise the total white blood cell count. These values are reported as a percentage of the total number of cells.

Cell Type% Of Total WBC's
Neutrophils47% to 77% (elevated in infection, inflammation, and stress)
Bands0% to 3% (elevated in some cases of bacterial infection)
Lymphocytes16% to 43% (elevated in some cases of viral infection and some leukemias)
Monocytes0.5% to 10% (elevated in some viral, fungal & TB infections, lupus, cancer)
Basophils0.3% to 2% (elevated in some leukemias, some cancers, and hypothyroidism)
Eosinophils0.3% to 7% (elevated in some allergies, cancer, leukemia, Hodgkin's disease, autoimmune disease)

Platelets are the smallest of the blood cells. They play an essential role in the blood clotting system. A platelet count: 150,000-400,000 per cubic millimeter is considered a normal range.

Last Updated: Oct 1, 2010 References
Authors: Stephen J. Schueler, MD; John H. Beckett, MD; D. Scott Gettings, MD
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PubMed Weak Immune System References
  1. Mayo J, Collazos J, Martinez E. Fever of unknown origin in the setting of HIV infection: guidelines for a rational approach. AIDS Patient Care STDS. 1998 May;12(5):373-8. [11361973]
  2. Perrone J, Hollander JE, Datner EM. Emergency Department evaluation of patients with fever and chemotherapy-induced neutropenia. J Emerg Med. 2004 Aug;27(2):115-9. [15261351]
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