CD4 and allergic disease: Regarding regulatory CD4+ T cells, the severity of allergic reactions has been associated with functional damage of allergen-specific Treg cells (CXCR5-FoxP3+IL-10+), Tr-1 (CXCR5-FoxP3-IL-10+) and, mainly in IgE-mediated disorders, TFR (CXCR5+FoxP3+IL-10+) (21, 22).