Immune complex, also known as antigen-antibody complex, occurs from the bonding of an antibody to an antigen. An antigen is any substance that is capable of causing the body to produce an antibody. Examples include toxins, microorganisms, and proteins that are foreign to the body. An antibody is a specific immune protein that is produced in the body because of the antigen. Immune complex molecules help in fighting diseases, but sometimes individuals form autoantibodies that attack the person’s own tissues and cause autoimmune diseases.
The bonding of the antigen and antibody is an important part of a healthy immune system. For example, if a person is exposed to a disease-causing organism, the white blood cells, also known as B cells, will cause the production of an antibody. The new molecule composed from the bonding of an antigen and an antibody is an immune complex. Usually, macrophages in the spleen and Kupffer cells in the liver remove these molecules. Macrophages, a term composed from the Greek words for big and eaters, are white blood cells that reside within tissue.
Phagocytes, or macrophages, consume and digest immune complex molecules. This is important in providing both innate and adaptive immunity. One macrophage can eat more than 100 bacteria before dying. If the immune complex clusters are not removed by macrophages or Kupffer cells, they then continue circulating. Eventually, they become trapped in human tissue and can cause autoimmune disorders, infections, and malignancies.
Many different diseases can occur when immune complex molecules build up in the bloodstream or tissues. Some that are well-known include Type I diabetes, Crohn’s disease, psoriasis, malaria, and viral hepatitis. In Type I diabetes, the antigen-antibody complex causes an autoimmune destruction of insulin-producing beta cells in the pancreas. When the molecules cause an autoimmune disease that inflames the intestines, it is known as Crohn’s disease.
Guillain-Barré syndrome, Addison's disease, and Sjogren’s syndrome are also autoimmune diseases that are less well-known. Altogether, there are more than 80 autoimmune diseases. Some researchers believe that chronic fatigue and fibromyalgia may be diseases caused by immune complex molecules that were not effectively removed from the body.
In a paradoxical fashion, immune complex molecules can either aid the body in the functioning of a healthy immune system or can cause harm. An antibody bonding with an antigen can be extremely helpful in fighting off illnesses or removing toxins from the body. A healthy immune system depends on these molecules forming. If, however, these molecules are not filtered from the body by macrophages or Kupffer cells, many varied diseases can occur.