Overview
HLA-B27 belongs to the human Major Histocompatibility Complex (MHC). It is a surface protein found on almost all body cells that helps the immune system distinguish between self and non-self tissue. The presence of this specific antigen is strongly associated with a group of conditions known as spondyloarthritides.
6p21.33 (Chromosome 6)
Immune System
Autosomal dominant (with variable penetrance)
8-10% in Central and Northern Europe
Function & Significance
The primary task of HLA-B27 is to present fragments of proteins (antigens) on the cell surface so that T-killer cells can inspect them. In HLA-B27-positive individuals, the immune system tends to misidentify certain harmless or self-structures as a threat, leading to chronic inflammation.
⚠️ Ankylosing Spondylitis (Morbus Bechterew)
About 90-95% of all patients with ankylosing spondylitis carry the HLA-B27 antigen. Important: Most carriers of HLA-B27 never become ill (only about 2-5% develop the disease). Presence alone is not a diagnosis, but a strong risk factor.
🧬 Relevant Marker
In genetic testing, a specific tag-SNP is often used, which almost always occurs together with the HLA-B27 allele:
6:31324200
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Significance:
This SNP is used as an indirect marker for HLA-B27 status. The G allele indicates the presence of HLA-B27 with very high probability.
📚 Data Sources
- OMIM: #142830 – Major Histocompatibility Complex, Class I, B; HLA-B
- dbSNP: rs4349859
- ACR: American College of Rheumatology – Spondyloarthritis Guidelines
Biological Function
Associated Conditions
Analyzed Markers
Strong genetic marker for the presence of the HLA-B27 allele.