Allergen-specific T cell quantity in blood is higher in allergic compared to nonallergic individuals

A total of 52 allergic individuals and 32 nonallergic individuals were studied. The allergen-specific B and Th cells were enumerated by culturing CFSE-loaded blood mononuclear cells for 7-days with allergen (cat, Timothy or birch), and determining the number of proliferating B or Th cells (diluting CFSE) by flow cytometry. Allergen-specific IgE concentration was determined by fluorescent enzymoimmunoassay (FEIA).The quantities of proliferating Th cells but not proliferating B cells specific for cat, Timothy and birch were significantly higher in cat-, Timothy- and birch-allergic individuals compared to nonallergic individuals. The titer of allergen-specific IgE showed significant correlation with allergen-specific Th cells and not with allergen-specific B cells for all 3 allergens.A high number of allergen-specific proliferating Th cells, but not proliferating B cells, may play a role in the pathogenesis of allergic asthma/rhinitis/eczema.Enhanced production of allergen-specific IgE is characteristic for allergic asthma, rhinitis or eczema [1,2]. Upon inhalation, ingestion or transcutaneous diffusion of the allergen, dendritic cells present peptides from the allergen to allergen-specific Th cells. These allergen-specific Th cells, expressing CD40 ligand and secreting Th2 cytokines like IL-4, stimulate the differentiation of allergen-specific B cells to IgE-producing plasma cells [3-6]. The increased production of IgE could be due to 1) increased quantity of allergen-specific B cells, 2) abnormal function of allergen-specific B cells (abnormally high B cell-intrinsic drive to differentiate into IgE plasma cells), 3) increased quantity of allergen-specific Th cells, 4) abnormal function of allergen-specific Th cells (abnormally high propensity to stimulate B cell differentiation into IgE plasma cells, eg, through increased secretion of Th2 cytokines), or 5) other mechanisms. To determine whether the mechanism of increased B cell quantity or the mechanism of increased