Chitine: Prudence quand même ?

 Chitin and Its Effects on Inflammatory and Immune Responses

Elieh Ali Komi D et Al. Clin Rev Allergy Immunol. 2018 Apr;54(2):213-223

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Les pansements hémostatiques à base de chitine sont largement utilisés et ne semblent pas actuellement poser de problème allergique (1). Néanmoins se pose la question de leur innocuité immune. Le développement des allergies croisées avec les produits dérivés de la mer et l'emploi de chitine comme complément alimentaire sont autant de facteurs de rencontre avec un allergène vrai. De telles allergies croisées s'observent également avec d'autres composants tels que la paravalbumine et le collagène des produits de la mer. Les pansements hémostatiques ne contenant pas de chitine ne semble pas exposer à ce risque potentiel.

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Chitin, a potential allergy-promoting pathogen-associated molecular pattern (PAMP), is a linear polymer composed of N-acetylglucosamine residues which are linked by β-(1,4)-glycosidic bonds. Mammalians are potential hosts for chitin-containing protozoa, fungi, arthropods, and nematodes; however, mammalians themselves do not synthetize chitin and thus it is considered as a potential target for recognition by mammalian immune system. Chitin is sensed primarily in the lungs or gut where it activates a variety of innate (eosinophils, macrophages) and adaptive immune cells (IL-4/IL-13 expressing T helper type-2 lymphocytes). Chitin induces cytokine production, leukocyte recruitment, and alternative macrophage activation. Intranasal or intraperitoneal administration of chitin (varying in size, degree of acetylation and purity) to mice has been applied as a routine approach to investigate chitin's priming effects on innate and adaptive immunity. Structural chitinpresent in microorganisms is actively degraded by host true chitinases, including acidic mammalian chitinases and chitotriosidase into smaller fragments that can be sensed by mammalian receptors such as FIBCD1, NKR-P1, and RegIIIc. Immune recognition of chitin also involves pattern recognition receptors, mainly via TLR-2 and Dectin-1, to activate immune cells to induce cytokine production and creation of an immune network that results in inflammatory and allergic responses. In this review, we will focus on various immunological aspects of the interaction between chitin and host immune system such as sensing, interactions with immune cells, chitinases as chitin degrading enzymes, and immunologic applications of chitin.