IL5 and Airway obstruction: Levels of SP are increased in induced sputum and correlated with airway obstruction, and CGRP level is elevated in bronchoalveolar lavage fluid.152,153 Neuropeptide release by sensory neurons positive for TRPA1 or TRPV1, which are markers of nociceptors, may play a particularly important role in this setting.154,155 For example, in cultured vagal ganglia nociceptive neurons, IL-5 stimulates the release of neuropeptides, such as VIP, that stimulate CD4-positive T cells and ILC2s, which in turn release type 2 cytokines such as IL-5, thereby amplifying allergic inflammation.