Figure 2.

The relationship of allergen-induced, type 2 immune responses and the nasal nervous system. Trigeminal fibers are responsible for tactile sensitivity, including nociception, and release such neuropeptides as substance P, neurokinin A, CGPR, and possibly NMU (see text). These mediators induce vasodilation and directly activate cytotypes involved in the inflammatory response, for example, mast cells, eosinophils, lymphocytes, and macrophages. Parasympathetic postganglionic fibers release acetylcholine and induce vasodilation and mucus production, while norepinephrine from sympathetic fibers may induce vasoconstriction by interacting with α-adrenergic receptors, which typically prevails over vasodilation induced by concomitant ligation of β-receptors.