It’s not because I specifically wanted one. I have a nickel allergy that makes me sensitive to pretty much everything else. Apparently an estimated 65 million other Europeans are also sensitive to nickel.
A recent paper* in Nature Immunology has found the culprit: Toll-like receptor (TLR) 4. The TLR family of proteins play an important role in microbial recognition and activation of the innate immune response. TLR4 responds to lipopolysaccharide (LPS), a major component of the outer membrane of Gram-negative bacteria. The interaction between TLR4 and LPS triggers the production of chemicals that produce inflammation. Interestingly, the authors found that nickel can bind directly to human (but not mouse) TLR4, in an area distinct from the LPS-binding region, also triggering inflammation.
While it’s good to know how nickel sensitivity happens, this paper doesn’t explain why it only happens to some people. On the other hand, the good news for mice is that they can wear costume jewellery without any risk of contact dermatitis. Hurrah!
Schmidt et al (2010). Crucial role for human Toll-like receptor 4 in the development of contact allergy to nickel. Nature Immunology 11: 814-820.
*As an aside, the authors seem to have no idea how to properly analyse their data from a statistical point of view. Student’s t-test to analyse 12 groups? Unfortunately sloppy stats is fairly common, even for research published in high impact journals like Nature Immunology.