Causes of nickel allergy explored

Nickel allergy: causes apparently researched.

(16.08.2010) Around 65 million people throughout Europe suffer from nickel allergy, affecting about 10 percent of women and about 1 percent of men. For those affected, the contact with nickel - as contained in the alloys of many fashion jewelry accessories - causes itchy redness and swelling of the skin. Together with colleagues from the Universities of Mannheim, Freiburg, Münster and Munich, German scientists from the University of Gießen have now conducted a comprehensive investigation into the causes of the allergic reaction and their findings in the current issue of the specialist journal „Nature Immunology“ presented.

Decisive for the allergic reactions to nickel are therefore metal molecules that attach to a protein of the immune system, which actually serves to protect against bacteria. For some time, the physicians were aware of the fact that not antigens trigger the allergy but a reaction in the T cells. However, which pro-inflammatory signal also contributes to this was previously unknown.

The T lymphocytes, or T cells for short, form a group of white blood cells that is immune-protective and continuously migrates through the organism to monitor the membrane composition of the body cells for pathological changes. When cells become ill and one of the causative molecules on the surface of the diseased cell exactly matches the individual receptor of a T cell, and at the same time there is a costimulatory effect, certain genes in the cell nucleus of the T cell are activated. Subsequently, cell growth begins and the cell differentiates into T-killer cells (destroying the diseased cell); T helper cells (alarm with soluble messengers and attract additional immune cells) or regulatory T cells (prevent overarching attacks on intact body cells). Scientists now have the receptor on the surface of these T cells „TLR4“ discovered, which is equipped as a protein molecule for detecting certain bacteria. Thus, a characteristic molecule of bacteria, called lipopolysaccharides (LPS), fits exactly into a recognition site of TLR4. However, nickel ions, which can dissolve when carried from nickel-containing alloys, also attach to the TLR4 receptors and, like the bacteria, trigger a reaction that can lead to severe inflammation and swelling at the contact site (contact dermatitis). .

The research team around Prof. Dr. med. Matthias Goebeler and dr. Marc Schmidt also found that the mechanism of action of TLR4 on nickel is different than that of bacteria, since the metal ions are attached elsewhere on the receptor. Thus, theoretically, it would be possible to block the attachment of nickel molecules without compromising the sensitivity of the receptor for LPS and thus for invading bacteria. This could be a breakthrough in the treatment of nickel allergy, as it is generally possible to develop specific TLR4 inhibitors that will prevent an allergic reaction in the future.

However, the most interesting concurrent result of the study was that in tested mice, no allergic reaction to nickel was triggered by TLR4 receptors, i. H. the experiments on animals do not allow any statement about the effect on the human body. The common practice of investigating allergy-promoting chemical substances in animal models is therefore to be treated with great caution, according to the statement of the scientists. (Fp)

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