As an atopic disorder, AD is classically considered a type 2‐driven immunopathology involving type 2 T helper (Th2) cells, interleukin (IL)‐4, IL‐5, IL‐9, and IL‐13, as well as IgE, mast cells, basophils, and eosinophils—with more recent data expanding this view to include Th17 and IL‐22 cellular responses in the genesis of AD.12 While T cells are promoting inflammation in certain instances,13, 14, 15 they are largely dispensable in the Flgft/ft model. Here, IL9 is linked to Alzheimer disease.