Dietary Chitin Particles Called Mimetic Fungi Ameliorate Colitis in Toll-Like Receptor 2/CD14- and Sex-Dependent Manners.

Chitin is a natural -acetylglucosamine polymer and a major structural component of fungal cell walls. Dietary chitin is mucoadhesive; anti-inflammatory effects of chitin microparticles (CMPs; 1- to 10-μm diameters) have been demonstrated in models of inflammatory bowel disease (IBD). The goals of this study were to assess (i) whether CMPs among various chitin preparations are the most effective against colitis in male and female mice and (ii) whether host chitin-binding Toll-like receptor 2 (TLR2) and CD14 are required for the anti-inflammatory effect of chitin.

Phagocytosis-mediated M1 activation by chitin but not by chitosan.

Chitin particles have been used to understand host response to chitin-containing pathogens and allergens and are known to induce a wide range of polarized macrophage activations, depending, at least in part, on particle size. Nonphagocytosable particles larger than a macrophage induce tissue repair M2 activation. In contrast, phagocytosable chitin microparticles (CMPs, 1-10 μm diameters) induce M1 macrophages that kill intracellular microbes and damage tissues.