Cleavage of Fibrinogen by Proteinases Elicits Allergic Responses Through Toll-Like Receptor 4

Abstract

Allergy Induction Proteinases found in fungi and other allergens elicit allergic inflammation, but how they do so is far from clear. It is also unclear how pattern recognition receptors, which detect invading microbes, drive allergic inflammation. Millien et al. (p. 792 ) shed light on this puzzle by showing that, in mice, induction of allergic inflammation requires proteinase-dependent cleavage of the clotting factor fibrinogen, leading to generation of a ligand that activates the pattern-recognition receptor, Toll-like receptor 4 (TLR4). Cleaved fibrinogen signals through TLR4 to activate the innate immune system and recruit cells to the airway, which drives both allergic responses and antifungal immunity.