IGHE and Allergy: However, serum IgE levels in patients with IgG4-RD with allergy/atopy was higher than in those without (p=0.0255) (see online supplementary figure S3); consistent with Della Torre et al20 Therefore, it is plausible that elevated serum IgG4, resulting from polyclonal expansion of many IgG4 B cells irrespective of antigen specificity, may be linked to IgE B cell expansion in a subset of allergic/atopic individuals with IgG4-RD.