title: Role of IL-13 in CD4 T cell-dependent IgE production in atopy.
abstract: IgE isotype switching of human B cells requires physical interaction of T and B cells via surface molecules, and either IL-4 or IL-13 secreted by T cells. In this study we analyzed the role of IL-4 versus IL-13 in IgE production in atopy. We found that peripheral blood mononuclear cells (PBMC) from atopic individuals but not from nonatopic subjects secreted IgE without addition of IL-4 or IL-13, if T and B cells were simultaneously activated by anti-CD3 mAb and soluble CD40L, respectively. IgE production by atopic PBMC was dependent on endogenously secreted IL-4 and IL-13, since it could be blocked by a combination of anti-IL-4 plus anti-IL-13 antibodies. No differences in the B cell compartment of nonatopics and atopics were detectable, since PBMC from both donor populations secreted comparable amounts of IgE, if only the B cells were activated by soluble CD40L plus either exogenous IL-4 or IL-13. Further phenotypic analysis of T cells from atopics revealed that activated CD4+45RO- secreted IL-4 but no IL-13, whereas CD4+45RO+ memory T cells secreted low amounts of IL-4, but large amounts of IL-13. Accordingly, prolonged activation of native CD4+45RO- T cells in vitro induced expression of CD45RO, and strongly favored secretion of IL-13 rather than IL-4. Addition of exogenous IL-4 during activation further increased both IL-4 and IL-13 production to a similar degree. However, the potential of CD4 T cells from atopics to deliver contact-dependent activation signals to B cells and to induce IgE production (in the absence of soluble CD40L) increased with prolonged activation, and coincided with IL-13 rather than IL-4 production. Under similar conditions, CD8 effector cells secreted IL-13 but no IL-4, did not express CD40L, and could not help Ig(E) production by B cells. These results suggest that, in atopy, persistently stimulated CD4+45RO+memory/effector T cells provide contact-dependent activation signals to B cells, and that these cells may induce IgE switching largely via secretion of IL-13.
authors.affiliation: Department of Asthma/Allergy Research, Pharmaceuticals Division, Ciba-Geigy, Basel, Switzerland.
authors.forename: F
authors.initials: F
authors.lastname: Levy
authors.forename: C
authors.initials: C
authors.lastname: Kristofic
authors.forename: C
authors.initials: C
authors.lastname: Heusser
authors.forename: V
authors.initials: V
authors.lastname: Brinkmann
mesh_terms: D000328:Adult; D001249:Asthma / Q000276:immunology*; D001402:B-Lymphocytes / Q000276:immunology; D017252:CD3 Complex / Q000276:immunology; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology*; D019013:CD40 Antigens / Q000276:immunology; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology; D018920:Coculture Techniques; D004797:Enzyme-Linked Immunosorbent Assay; D005434:Flow Cytometry; D006801:Humans; D007073:Immunoglobulin E / Q000096:biosynthesis*; D018793:Interleukin-13 / Q000502:physiology*; D015847:Interleukin-4 / Q000502:physiology; D017493:Leukocyte Common Antigens / Q000276:immunology; D008213:Lymphocyte Activation; D012221:Rhinitis, Allergic, Perennial / Q000276:immunology*; D006255:Rhinitis, Allergic, Seasonal / Q000276:immunology*
chemical_list: D017252:CD3 Complex; D019013:CD40 Antigens; D018793:Interleukin-13; D015847:Interleukin-4; D007073:Immunoglobulin E; D017493:Leukocyte Common Antigens