Role of chitin and chitinase on allergic immune response

Chitin is found in the sheats of parasitic nematodes, in the exoskletons of crustaceans and insects, in the fungal cell walls, but not in mammals. Chitinases are induced in lower life forms during infections with these agents. Chitinase production is an important feature of antiparasitic response against chitin containing organisms. Although chitin itself does not exist in humans, chitinases are present. There is very limited knowledge on the biological roles of human chitinases and the role of these enzymes in antiparasitic response in humans remains to be defined. Together with the Th2 type response, IgE production and eosinophil activation are also main components of antiparasitic defense. Most of the parasites contain chitin and in addition to these, house dust mite, cockroach, fungi, which are common causal allergens also contain chitin. These evidence lead us to a novel hypothesis about allergic diseases; i.e. immun system senses chitin as if there is a parasite or fungi infection, and responds with a Th2 polarised immune reaction accordingly. In this study, we investigated in vitro effects of chitin or chitin microparticles on peripheral blood mononuclear cells by Elisa and Elispot technique. We stimulated these cells with various stimulations at different times and investigated AMCase gene expression in skin biopsies taken from atopic dermatitis patients. We compared AMCase gene products with β-actin. We observed a positive TNF-α, IFN-γ and poor IL-13 response but no IL-4 response with chitin microparticle stimulation. We also observed that the mononuclear cells, precipitated from peripheral blood, expressed AMCase but no stimulators (PHA, Chitin, CMP) changed this expression. In AD patients, AMCase production was higher in healthy regions of skin than in skin of atopic lesion. AMCase gen expression was isolated in healthy and atopic skin regions. In opposition to current expectations, it can be assumed that the production of this enzyme is not limited to stomach and lung tissues. As there are various types of AMCases in human body, and because there are different entrances for allergens that use different pathways, we need more in vitro datas derived from human cells.