TYPE 2 IMMUNE RESPONSES IN THE CONTEXT OF HELMINTH INFECTION, ASTHMA, DENDRITIC CELLS, AND MYELOID DERIVED SUPPRESSOR CELL FUNCTION

Type 2 (TH2) immune responses evolved to respond to helminth parasite infections by the production of TH2 cytokines, which stimulate anti-helminth immunity. Macrophage migration inhibitor factor (MIF) is a pleiotropic cytokine, which is produced by many cell types. We demonstrate that mice deficient in MIF have enhanced clearance of a helminth parasite. MIF deficiency in CD4+ T cells was found to be the most important for mediating parasite clearance. We mimicked MIF deficiency by administering an inhibitor of the MIF tautomerase activity, sulforaphane, and this also increased parasite clearance (Section I). TH2 immune responses underlie allergy and allergic asthma, in which the same cytokines that help expel parasites are released in response to innocuous substances. Integral to the initiation of adaptive TH2 immunity are dendritic cells (DCs), which take up antigen and stimulate antigen-specific CD4+ T cell responses. We found that DC expression of ADAM10, a zinc-dependent metalloproteinase, is critical for the development of TH2 immune responses and IgE production from B cells. This effect is demonstrated in both allergic airway inflammation and anaphylaxis models. ADAM10-deficient DCs are unable to cleave Notch1 receptors, resulting in reduced IL-6 production and this ultimately results in decreased TH2 activity. ADAM17 is closely related to ADAM10 in both structure and function. Interestingly, mice from which ADAM10 and 17 are removed from DCs (ADAM10/17DC-/-) have a distinct phenotype from both ADAM10DC-/- and ADAM17DC-/- mice in models of allergic airway inflammation (Section I). We also examined another effect of TH2 cytokines on the interaction between mast cells and myeloid derived suppressor cells (MDSCs). We sought to understand how histamine and IL-13, mediators made by mast cells, affect the immunoregulatory function of MDSCs. MDSCs in IL-13-deficient mice with tumor are more prevalent in circulation rather than in tumor or organs, which could be due to changes in CCL2/CCR2 chemotaxis. In addition, MDSC function after treatment with the DNA methyltransferase inhibitor, decitabine was examined. This treatment reduced their suppressive function and increased the expression of molecules needed for antigen presentation. Overall, TH2 immunity has multifaceted roles in anti-parasite immunity, allergic asthma, and MDSC function (Section II)