Human leukocyte antigen B27

Human Leukocyte Antigen B27 (HLA-B27) is a protein that plays a critical role in the immune system. It is part of a family of genes called the human leukocyte antigen (HLA) system which helps the immune system distinguish the body's own proteins from proteins made by foreign invaders such as viruses and bacteria. HLA-B27 is a specific protein within this system, found on the surface of white blood cells.

Association with Diseases

HLA-B27 is best known for its association with a group of autoimmune diseases termed spondyloarthropathies, which primarily affect the spine and other joints. This group includes:

• Ankylosing spondylitis (AS)
• Reactive arthritis (formerly known as Reiter's syndrome)
• Certain forms of juvenile rheumatoid arthritis
• Psoriatic arthritis

Individuals who carry the HLA-B27 antigen are at a higher risk of developing these conditions, although not everyone with HLA-B27 will develop an autoimmune disease. The presence of HLA-B27 is used in conjunction with other clinical findings to help diagnose these conditions.

Genetic Aspects

HLA-B27 is a genetically inherited protein. The gene that codes for HLA-B27 is located on chromosome 6. There are several subtypes of the HLA-B27 gene, with some subtypes being more strongly associated with autoimmune diseases than others.

Testing for HLA-B27

Testing for the presence of the HLA-B27 protein is often done through blood tests. This can be helpful in diagnosing conditions like ankylosing spondylitis, especially in the early stages of the disease when X-rays may not show changes in the joints or spine.

Role in Disease Mechanism

The exact role of HLA-B27 in the development of autoimmune diseases is not fully understood. It is believed that HLA-B27 may present a specific peptide or group of peptides to T-cells, triggering an immune response that mistakenly targets the body's own tissues, leading to inflammation and disease.

Treatment and Management

There is no cure for the autoimmune diseases associated with HLA-B27, but treatments are available to manage symptoms and slow disease progression. Treatment options may include nonsteroidal anti-inflammatory drugs (NSAIDs), tumor necrosis factor (TNF) blockers, physical therapy, and in some cases, surgery.

Conclusion

HLA-B27 is a significant marker in the field of immunology and rheumatology, providing insights into the genetic predisposition to certain autoimmune diseases. While the presence of HLA-B27 can indicate a higher risk for developing specific conditions, it is just one factor among many that healthcare providers consider when diagnosing and treating patients.