Immune Deficiency Leads to Infections

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Category: Immunodeficiency Articles Published on Monday, 14 July 2008 Written by Yong Tsai, MD
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Tom, 30, has had four episodes of pneumonia over the last four years. He also has had chronic sinusitis since age 10, routinely treated with multiple antibiotics.   John, a 26-year-old male intravenous drug abuser, has developed an unusual fungal infection in his lung.
What is the common denominator that relates each patient's condition? Each suffers different infections that result from different immune deficiency diseases.

The immune system is just like an internal security force of cells (or protein) that constantly checks microorganisms and other foreign materials entering our body. The immune system stands ready to destroy those invaders, if necessary.  But, when part of the immune system is absent, or its function is hampered, an immune deficiency disease may result.

The major components of our immune system are B-lymphocytes, T-lymphocytes, phagocytes, and compliment cells.  B-lymphocytes (sometimes called B-cells) primarily produce antibodies-proteins that can recognize microorganisms as foreign.  They physically attach to the microorganism and set off a complex chain of reactions involving other components the immune system to destroy the microorganism.  Antibodies also are called immunoglobulins are grouped into four classes-IgM, IgG, IgG, IgA, and IgE.

IgM is formed very early in infection, an early defense mechanism, IgG, found in the blood stream and tissue, plays a major role in defending particularly against bacteria.
IgA are produced near mucus membranes and secrete into mucus, tears, bile, and saliva, where they ultimately protect against infection in the respiratory passages and intestines. IgE is responsible for allergic reactions.

The body's complement system, meantime, is composed of 18  serum proteins which function in an ordered and integrated fashion to defend against infection. Phagocytes ingest and kill microorganisms.  Bacteria, then, are destroyed by the cooperative efforts of antibody, complement and phagocytes.

T-lymphocytes (T cells) are another type of immune cell, but  T-cells do not produce antibodies. They can directly attack organisms such as viruses, fungi, or parasites, and can regulate the immune system.

Some immune deficiency diseases are relatively common, while others are rare. An immune deficiency disease may be caused by either an intrinsic (inborn) defect in the immune system, an extrinsic (outside) environmental factor (HIV infection), or agent (radiation or chemotherapy).  Hallmarks of immune deficiency are recurrent or unusual infections that rarely cause problems for the healthy.   Patients with B-cell immune deficiency, for example, have recurrent bacterial infections, while patients with T-cell immune deficiency have viral, fungal, and even parasitic infections.

Early detection of immune deficiency-coupled with proper treatment options-has significantly improved the life of many patients.

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