Figure 2.
Chitin regulation of macrophage proinflammatory [tumor necrosis factor (TNF)-α] and anti-inflammatory [interleukin (IL)-10] cytokine production. Chitin stimulates the expression of TNF-α and IL-10 in a size-dependent manner. Large chitin is inert, and intermediate-sized chitin (40–70 µm) is a powerful stimulator of TNF. This activation is mediated mainly via a Toll-like receptor-2–nuclear factor-κB (TLR-2-NF-κB) pathway, with lesser contributions from spleen tyrosine kinase (Syk). In contrast, small chitin (<40 µm, usually 2–10 µm) is a potent stimulator of IL-10 production. This inductive event is mediated largely via a dectin-1-Syk pathway, with lesser contributions from TLR-2 and NF-κB.