HLA-B27

HLA-B27 is a variant of the human protein complex human leukocyte antigen -B ( HLA -B). HLA-B belonging to the group of MHC class I- protein complexes that are located on the surface of nearly all cells of the organism and regulate important functions of the immune system. MHC complexes present short protein segments (antigens) on the cell surface, where they can be bound by T-lymphocytes. Mutations in the HLA-B gene may be associated with certain autoimmune diseases ( spondyloarthropathy ).

Generally

The HLA-B gene is located on chromosome 6p21.33, and consists of a group of at least 31 very similar alleles, which are referred to as HLA- B2701 and HLA- B2728. The frequency of HLA-B27 in the European population is about 8 %, but may be up to 14% in certain areas like Finland.

Medical importance

Very strongly associated HLA- B27 is a group of certain autoimmune diseases such as rheumatoid arthritis ( " classical rheumatism" ) and some diseases from the group of seronegative Spondylarthritiden. For this reason, the distinction in HLA -B27 - positive and-negative patients in rheumatology is an important criterion in the differential diagnosis.

In its function to the immune system seems to be particularly effective HLA-B27 binding specific viral antigens compared to the other proteins of the HLA class 1. It has been shown that HIV-infected carriers of HLA-B27 show a significantly delayed onset of AIDS. Also, components of influenza A viruses are particularly well bound by HLA -B27. The downside of this feature of HLA -B27 could pose this very association with the autoimmune diseases mentioned above.

Associated diseases

Detection of HLA -B27 in a healthy person does not mean that she has any of the following diseases or cancer. For example, carry about 90% of patients with ankylosing spondylitis these MHC - I- property, but the prevalence of this disease in Europe is around 0.5 to 1 %. However, the detection of this marker in a patient makes certain spinal problems likely diagnosis.

The following diseases have so far been associated with HLA -B27:

  • Ankylosing spondylitis (Bechterew's disease ) (90 %).
  • Reiter's disease (70-80%)
  • Psoriatic arthritis ( 60-70%)
  • Juvenile idiopathic arthritis with enthesitis (75%)
  • Inflammation of the anterior portion of the eye: Acute anterior uveitis, iritis, iridocyclitis, or ( about 50%)

Since the first discovery of the association of HLA -B27 with ankylosing spondylitis in 1973, different hypotheses have been proposed about the cause of this relationship with certain autoimmune diseases. These hypotheses range from genetic linkage with a disease gene via the binding of autoimmune antigens to malfunction of HLA -B27 itself and could not yet be clarified. It is now thought of a direct involvement in the diseases of HLA -B27, as transgenic animals with the HLA -B27 gene have similar symptoms. In addition, other genes have been discovered in the meantime, which are directly related to certain medical conditions, such as a variant of the interleukin -23 receptor in ankylosing spondylitis.

Extenders levamisole in cocaine

In people who are carriers of HLA -B27, which is often fatal agranulocytosis may occur, which is why levamisole is not commercially available. The most dangerous side effects are aplastic anemia and vasculitis, and also by the reduction of levamisole to Aminorex, pulmonary hypertension. Increasing the addition of levamisole is seen to cocaine as a diluent, which is present with an average percentage of 7.7 % was found in about 60 % of the samples. Cocaine users should be tested for HLA -B27.

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