B27

B27 or HLA-B27 is a human leukocyte antigen serotype within HLA-B serotype group. B27 is a split antigen of the broad antigen HLA-B7, and is a member of the HLA-B locus of the major histocompatibility complex (MHC) on chromosome 6. HLA-B27 is strongly associated with ankylosing spondylitis, and other associated inflammatory diseases referred to as "spondyloarthropathies".

Structure and Function

HLA-B27 is a protein that plays a vital role in the immune system. It is a part of the HLA-B gene family, which provides instructions for making a group of related proteins known as the human leukocyte antigen (HLA) complex. The HLA complex helps the immune system distinguish the body's own proteins from proteins made by foreign invaders such as viruses and bacteria.

Clinical Significance

HLA-B27 is associated with a number of autoimmune diseases, including ankylosing spondylitis, reactive arthritis, psoriatic arthritis, and uveitis. The presence of HLA-B27 is not a diagnostic test but can be used to support a suspected diagnosis of these conditions.

Ankylosing Spondylitis

Ankylosing spondylitis is a type of arthritis that affects the spine. Symptoms include pain and stiffness from the neck down to the lower back. The spine's bones (vertebrae) may grow or fuse together, resulting in a rigid spine.

Reactive Arthritis

Reactive arthritis is a condition that causes inflammation in various places in the body. The areas most commonly affected are the knees, feet, and hands. It often develops following an infection, particularly a sexually transmitted infection or a bowel infection.

Psoriatic Arthritis

Psoriatic arthritis is a form of arthritis that affects some people who have psoriasis — a condition that features red patches of skin topped with silvery scales. Most people develop psoriasis first and are later diagnosed with psoriatic arthritis, but the joint problems can sometimes begin before skin patches appear.

Uveitis

Uveitis is inflammation of the uvea, the middle layer of the eye. The uvea consists of the iris, choroid and the ciliary body. Uveitis can have many causes, including eye injury and inflammatory diseases. Exposure to toxic chemicals such as pesticides and acids used in manufacturing processes also can cause uveitis.

See Also

• Human leukocyte antigen
• Major histocompatibility complex
• Autoimmune disease

B27 Resources
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