Cocultures from AD patients with IL-9 production also showed increased levels of Th2, Th1, and Th17/22 cytokines in response to HDM, except for IL-31 and IL-21 in the CLA− compartment since the former is CLA+-specific [28] and the latter is produced more by CLA+ T cells [49]. Here, IL21 is linked to Alzheimer disease.