In genetically engineered mouse models lacking Tfr cells, antigen-specific B cell responses are elevated both in vitro and in vivo following immunization with protein-hapten conjugates and in a house dust mite challenge allergy model (43, 49), with other work revealing reduced antigen-specific IgE and IgG titers in Tfr-deficient mice in food allergen sensitization and immunization settings, respectively (50, 51). Here, TFRC is linked to allergic disease.