IGHE and Alzheimer disease: In AD, IL‐4 and IL‐5 are mainly secreted by Th2 cells, and the secreted cytokines stimulate B cells to secrete IgE, which affects IgG1 and IgG2a levels and the production of various inflammatory cytokines (Bieber, 2008; Dokmeci & Herrick, 2008; Muñoz et al., 2017).