Chitin is the second most abundant
polysaccharide in the world; it is found in insects, parasites and fungi.
Chitinases break down
chitin, and are a part of the defence mechanism against
chitin-containing parasites in lower life forms. This review is based on the results of PubMed-searches using the search-terms:
chitin,
chitinase,
allergy and
asthma. Research in murine models has proved that
chitin is a size-dependent microbial-associated molecular pattern, with the ability to induce an immunological response via
pattern recognition receptors. Medium-sized
chitin micro-particles (CMPs) have been shown to induce
inflammation, while small-sized CMPs reduce
inflammation. The amount of acidic mammalian
chitinase correlates with
asthma, and the
enzyme has been shown to induce
chemokine secretion in murine lungs. The high prevalence of
asthma among people working with chitinous substances, such as crabs and fungi, supports the hypothesis that
chitin might be an
allergen playing a role of significance in the development of
asthma. This new knowledge about
chitin and
chitinases, combined with the hygiene-hypothesis, may contribute to a model for the pathogenesis of allergic conditions where
chitin and
chitinases are potential therapeutic targets.