MHH, Seminarroom h

Antigen + Basophils + CD4 + T cells  T H 2 cells IL-4 Fc  RI MHC II

representing less than 1% of circulating white blood cells susceptible to staining by base dyes Basophils appear in many specific kinds of inflammatory reactions can be found in unusually high numbers at sites of ectoparasite infection (e.g. ticks) basophils are primary effector cells in allergic disorders Basophils

Splenic Basophils in Strongyloides venezuelensis infected mice Higher percentages of Basophils in Strongyloides venezuelensis infected mice Baophils (0.2% naive, 5.84% inf.) Mastcells (0.02%naive, 0.39% inf.) Fc  RI + c-Kit - = Basophils Fc  RI + c-Kit + = Mast cells Strongyloides venezuelensis

Cytokine production of Basophils after Strongyloides infection in vitro Basophils from infected mice produce large amounts of „T H 2 cytokines“ Basophils + IL-3 (24h)

Same amount of MHCII expression on Basophils of naive and infected mice=  MHCII expression is no limiting factor for TH2 induction MHC II expression on Basophils

Ability of basophils to induce naive CD4 + T cells to develop into TH2 cells without IL4

with IL4 Ability of basophils to induce naive CD4 + T cells to develop into TH2 cells

 Basophils from infected mice are able to induce TH2 development without IL4 without IL4 with IL4 Ability of basophils to induce naive CD4 + T cells to develop into TH2 cells

Bone marrow basophils induce T H 2 cells in vitro Expression of MHC II and costimulatory molecules  Bone marrow basophils express MHCII, CD80, CD86

of IL4 -/- mice (G4/G4)Basophils of wt mice Basophils of wt mice are able to induce naive CD4+ cells to develop into TH2 cells Basophils produce sufficient IL-4 for maximum development of TH2 cells Bone marrow basophils induce T H 2 cells in vitro without IL4 with IL4

Basophils pulsed with antigen-IgE complexes are potent APCs Basophils + DNP-OVA + CD4 + T cellsT H 2 cells Basophils are able to process DNP-OVA into OVA(323– 339) and to display peptide fragment in association with MHC class II and to produce IL-4 The enhancing effect of IgE anti-DNP on basophil- induced T H 2 cell development was most apparent when basophils were pulsed with low concentrations of DNP-OVA Basophils + DNP-OVA + IgE anti DNP + CD4 + T cellsT H 2 cells - +

CD4 + T cells + OVA or DNP-OVA +/- IgE anti-DNP  These results suggest that basophils, taking advantage of their expression of Fc  RI, might efficiently take up low doses of antigen in an IgE-dependent way of DNP-OVA Proliferation assay of CD4 + T cells

APC activity of basophils and sorted CD11c + splenic DCs by changing the ratio of APCs to naive CD4 + T cells In presence of IgE-complex even low ratios of basophils induce T H 2 development

in vitroin vivo Basophils are able to induce naive CD4 + cells to develop into TH2 cells in vitro

OVA-pulsed basophils induce T H 2 cells in vivo Basophils + DNP-OVA + IgE anti DNP  mice + challenge with OVA  CD4 + T cells + OVA-pulsed  T–spleen cells Basophils induce T H 2 development in vivo

OVA-pulsed basophils induce T H 2 cells in vivo Basophils + DNP-OVA + IgE anti DNP  mice + challenge with OVA  CD4 + T cells + OVA-pulsed  T–spleen cells Basophils induce T H 2 development in vivo DCs induce T H 1 but not T H 2 development in vivo

OVA-pulsed basophils induce T H 2 cells in vivo Does OVA-pulsed basophils induce IgE and IgG1 production? OVA-pulsed basophils induce IgE and IgG1 production Basophils are important to induce T H 2 responses in vivo Basophils + OVA  mice

Intravenous administration of antigen-IgE complex induces T H 2 responses IC = Immune Complex (DNP-OVA + IgE anti DNP) MAR-1 = anti-Fc  RI  Basophils efficiently take up IC and induce T H 2 development in vivo Depletion of Basophils blocks T H 2 development and therefore IgG1 production of B cells What happens aftre depletion of basophils?

Intravenous administration of antigen-IgE complex induces T H 2 responses Does IL-3 administration increases the number of basophils? Higher numbers of basophils lead to increased production of IgE and IgG1 Yes, it does! Influence on Antibody production?

Summary Basophils produce large amounts of „T H 2 cytokines“ IL-4 and IL-13 after uptake of antigen Basophils are potent APCs Basophils are able to induce naive CD4 + cells to develop into TH2 cells Intravenous administration of antigen-IgE complex induces TH2 responses in vivo Antigen + Basophils + CD4 + T cells  T H 2 cells IL-4 Fc  RI MHC II

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