Genetics Cause for Arthrities
Recent evidence indicates that abnormalities of the immune system may be inherited or are genetic in nature. The discovery of human leukocyte antigens (HLA) could provide an important breakthrough, not only for arthritis sufferers but also for victims of other diseases, such as multiple sclerosis, some types of diabetes, and some types of leukemia. HLAs are a series of proteins on the surface of body cells that are determined by inheritance; the proteins on a person’s cells are inherited from his or her parents. Certain HLA proteins are present more frequently in individuals with certain forms of arthritis, suggesting that the tendency to develop some forms of arthritis may be inherited.
Some dramatic evidence that heredity plays a vital role in the development of many types of arthritis came during 1990 from the University of Texas Southwestern Medical Center and The Howard Hughes Medical Institute in Dallas, Texas. Researchers inserted two human genes into fertilized rat eggs, where the genes became part of the animals’ own genetic code. The two genes which have been linked to a group of arthritic diseases (ankylosing spondylitis, inflammatory arthritis, and arthritis associated with psoriasis and certain conditions associated with inflammation of the bowel) are identified as HLA-B27 and human beta-2 microglobulin. Together they produce a protein produce called B27. However, it remains to be determined exactly how the protein causes arthritic disorders.
The B27 is one of a number of molecules referred to as human lymphocyte antigens, which help regulate the white blood cells of the body’s immune defence system.
Researchers believed that these genes have long been the markers for some arthritis diseases, but were surprised to see the animals with the transplanted genes develop significant symptoms. However, mice transplanted with the human genes did not develop arthritic diseases. Estimates are that 7 to 8 percent of people worldwide carry the two genes and that their risk of developing an arthritic disease is one to 20 percent.
Additionally, a gene has been found in certain families that lead to increased risk of osteoarthritis because it causes a defect in the cartilage. Researchers hope that in the future, this gene can be modified and the defect corrected, thereby decreasing the risk of osteoarthritis in these people.
Better treatments for arthritis will become available as researchers develop more links between arthritis and genetics.
Thus the immune system with a genetic (inherited) tendency seems to be at work in some forms of arthritis. However, there still must be an unspecified trigger that sparks the chain reaction of self-destructive immune reactions leading to arthritis. Many researchers are trying to discover the identity of the antigens that trigger the immune system.