FCER2 and asthma: Der p 1 digests lung epithelium tight junctions (ZO-1) to increase accessibility of the allergen to the antigen presenting cells (APC) in the deeper tissue [10,11], cleaves low affinity IgE receptor (FcεRII or CD23) on human B cells and upset IgE regulation [12,13], cleaves α-subunit of human IL-12 receptor (CD25) on T cells leading to more IL-4 and less IFN-γ production [14], and digests α1-antitrypsin to promote airway inflammation and asthma [15].