Tom, a 30 year-old man, has had four episodes of pneumonia over the past four years.  He also has had chronic sinusitis since age 10, which was treated with multiple courses of antibiotics. After testing, his serum IgG, IgA and IgM result are in below normal range.

The major components of our immune system are B-lymphocytes, T lymphocytes, phagocytes and compliment.  B-Lymphocytes (sometimes called B-cells) produce anti-bodies. They can physically attach to microorganisms, such as bacteria, and set off a complex chain of reactions involving other components of the immune system that eventually destroy the microorganism.  

Antibodies are also called immunoglobulin, and are grouped into several major classes: IgG, IgA, IgM, and IgE.  IgG, found in the blood stream and tissues, play a major role in defending against microorganisms, particularly bacteria.  IgA are produced near mucus membranes and secrete into mucus, tears, bile, and saliva, where they protect against infection in the respiratory system and intestines.  IgM is formed very early in infection.

Immunoglobulin deficiency disease occurs when our bodies are unable to produce an adequate amount of immunoglobulin to fight against bacteria.  Some of immunoglobulin deficiency diseases are relatively common, such as IgA deficiency and common variable immunodeficiency (CVID). 

Individuals with selective IgA deficiency are deficient in IgA only. This deficiency is the most common of the immunodeficiency diseases, occurring in 1 in 500 people. The majority of IgA deficient patients are healthy and free of symptoms.  By contrast, some patients can have recurrent bacterial infections, such as sinus infection, more than three times a year or pneumonia more than twice a year. Currently, it remains impossible to replace IgA in selective IgA deficiency patients.

CVID is a common form of  immune deficiency disease.  The specific type of deficiency and its clinical courses is variable from patient to patient. A patient has increased  susceptibility to bacterial infections that may first occur in childhood. However, in the majority of patients, a CVID diagnosis is not made until the third or fourth decade of life.  Patients with CVID have markedly decreased serum immunoglobulin IgG, IgA and/or IgM levels.

Immunoglobulins  for replacement are pooled from the sera of as many as 60,000 screened donors, then processed and chemically purified. The final product, purified gamma globulin, consists mainly of IgG and only trace amounts of IgA and IgM.  Immunoglobulin replacement is typically given intravenously every three to four weeks. Most CVID patients respond very well to intravenous gamma globulin (IVIG) therapy.  

Early detection of immunoglobulin deficiency and the availability of effective treatments, such as immunoglobulin replacement and antibiotics, have greatly improved the outlook for patients with CVID and other immunoglobulin deficiency diseases.