NGF and asthma: By contrast with the immune imbalance in neutrophilic asthma,paucigranulocytic asthma may be more strongly associated with neural regulation as suggested by high levels of nerve growth factor (NGF) (54) and sphingolipid synthesis inhibition (55) induced AHR, and bronchoconstrictor signaling (56) are also involved in the pathogenesis of paucigranulocytic asthma.