Chitin May Be Responsible for Allergies to Shellfish, Dust, and Mold

Discussion in 'Fibromyalgia Main Forum' started by SpiroSpero, Oct 24, 2009.

  1. SpiroSpero

    SpiroSpero New Member

    Researchers at the University of California in San Francisco (UCSF)
    have discovered a strong association between chitin and allergy, as
    well as asthma. The results of these studies have been published this
    week in an early online version of the journal Nature, with a print
    version due soon.

    Chitin is a polysaccharide properly termed N-acetyl-B-D-glucosamine,
    and makes up the rigid exoskeleton of crabs, shrimp, and insects like
    dust mites. It is also found in various fungi and molds. While chitin
    is the most common biopolymer after cellulose, it is never found in
    organisms containing an internal skeleton, such as humans and other
    vertebrates. In fact, humans and other animals are genetically
    programmed to recognize the substance and eliminate it via an enzyme
    called acidic mammalian chitinase (AMCase). Unfortunately, a less
    active form of AMCase can also be activated, leading to inflammation
    and allergic response to chitin. In severe cases, asthma can result.

    For this study, Richard Locksley and his colleagues at UCSF sprayed
    aerosolized chitin into the lungs of laboratory mice. The mice
    developed an immediate immune response to the chitin, producing the
    inflammatory cytokines interleukin (IL) 4 and 13. White blood cells,
    termed eosinophils and basophils, then entered the lung tissue and
    mounted an attack against the chitin. This kind of acquired immune
    response would be expected if the mice had been previously exposed to
    chitin, but they had not. Furthermore, the rapid involvement of the
    interleukins and white blood cells is characteristic of a classic
    allergic response, which relies upon previous exposure to the

    To find out why the immune systems of mice acted as if they had seen
    the chitin before, Locksley and his team tested mice with and without
    a special type of white blood cell, called the macrophage. Unlike IL4,
    IL13, eosinophils or basophils, the macrophage is part of an
    organism's innate, rather than acquired, immune response. Upon
    bacterial or viral infection, the macrophage will become activated and
    ingest the invading particles, regardless of whether it has dealt with
    these particles in the past. Macrophages also produce different
    enzymes, such as AMCase, which they use to digest the ingested

    Mice without macrophages did not react against chitin, indicating that
    these cells are responsible for initiating the immune response.
    Furthermore, mice which produced a greater than average amount of
    AMCase showed a lowered acquired immune response to chitin. This
    suggests that AMCase, by quickly removing the stimulus from the
    system, dampens the body's acquired, and often allergic, response.

    Unfortunately, not all people have high levels of AMCase. Also, some
    people have AMCase variants, which do little to break down and digest
    chitin. These people may be at increased risk for developing allergy
    and asthma, especially if exposed repeatedly to high levels of chitin.
    For example, there are high rates of asthma among workers at shellfish
    processing plants, sometimes as much as 25%. In the population at
    large, allergic and asthmatic reactions to shellfish, insects, and
    molds are also on the rise. Locksley and his group hope to test
    individuals with allergies to chitin, to help determine if they carry
    these less active AMCase variants.

    One reason for the increasing rates of allergy and asthma among the
    general population is the increased microbial sterility of modern
    society due to widespread use of antibiotics. By eliminating bacteria
    that would feed on chitin, there may be an overabundance of this
    substance in the environment, resulting in increased exposure and
    immune reaction.
    While Locksley states that "asthma is increasing in all industrialized
    societies," he hopes that by elucidating the causes and mechanisms of
    allergy and asthma, new treatments can be developed soon.

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