The Reason for High Serum in IgG4

Antibodies or immunoglobulins are proteins produced by your immune system in response to foreign substances in your body. Microbes, including bacteria, viruses and fungi, toxins and other molecules that are not familiar to your body, can trigger an antibody response. Thus, antibodies, like IgG4, are a defense mechanism that helps to destroy and remove harmful particles from your body. However, antibodies can also play a role in autoimmune diseases and the presence of high serum IgG4 may be an indication of autoimmune pancreatitis.

White Blood Cells and Antibodies

• Antibodies are produced by white blood cells called B-lymphocytes or B-cells. B-cells can produce specific antibodies against, theoretically, an unlimited number of molecules. Each antibody recognizes a specific antigen, or a surface molecule on a bacteria. The antibody binds the antigen, which eventually leads to coating of the bacterial cell with several antibodies. In response, other white blood cells, like neutrophils or macrophages, can recognize and consume the antibody's coated bacterial cell. Thus, antibodies mediate the elimination of bacteria before they can cause a disease.

Types of Antibodies

• There are five classes or isotypes of antibodies named in humans. These are IgM, IgG, IgE, IgA and IgD. The IgG isotype is further divided into four subclasses named IgG1, IgG2, IgG3 and IgG4 and the IgA is divided into two subclasses named IgA1 and IgA2. The isotypes differ in their biological functions. For example, IgE is associated with allergy, IgA is involved in immune defense at mucosal surfaces and breast milk and IgG antibodies are commonly produced to battle microbes. In addition, IgG1, IgG3 and IgG4 antibodies can cross the placenta and protect the developing fetus.

Antibodies and Serum

• There are certain levels of IgG antibodies present in your blood at all times. The normal IgG levels in serum are 9 mg per ml of IgG1, 3 mg per ml of IgG2, 1 mg per ml of IgG3 and 0.5 mg per ml of IgG4. Increased levels of IgG antibodies in your serum may be an indication of a microbial infection. The most common antibodies produced in response to microbial protein antigens are lgG1 and lgG3, while IgG2 and IgG4 play only a minor role in defense against microbial antigens.

High Levels of IgG4 in Serum

• A study published in the October 2009 issue of the International Journal of Clinical Chemistry showed that serum IgG4 levels were elevated with patients suffering from autoimmune pancreatitis. Patients with autoimmune pancreatitis had an average serum IgG4 level of 3 mg per ml. This is highly elevated when compared to normal serum IgG4 levels. A review article published in the January 2009 issue of the Journal of Gastroenterology and Hepatology suggested that serum IgG4 levels should be used as a marker to diagnose autoimmune pancreatitis.

Autoimmune Pancreatitis

• According to the Mayo Clinic, autoimmune pancreatitis is an inflammatory disorder that affects the pancreas, bile ducts, salivary glands, kidneys and lymphatic system. Autoimmune pancreatitis is a reaction in which your immune system mistakenly attacks your own tissue. In general, autoimmune diseases, like lupus, diabetes and multiple sclerosis, occur when your B-cells produce antibodies that recognize and destroy your own cells.