MODULATION OF THE HUMAN IGE RESPONSE BY XENOBIOTICS

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This project will determine the mechanisms which aromatic hydrocarbons, such as those in air pollution, enhance human allergic antibody (IgE) responses and thereby contribute to the marked increase in allergic airway disease that has occurred this century. Epidemiologic data suggest that environmental factors play an important role in the increasing expression of allergic disease. Yet almost no attention has been given to directly testing if environmental influences, exemplified by the polycyclic aromatic hydrocarbons found in diesel exhaust (PAH- DEP), specifically after the IgE response nor to the basic mechanism by which this may occur. Knowledge about IgE regulation and consideration of the available epidemiologic data lead us to the seminal experimental discovery that PAH-DEP has direct immuno-enhancing effects on human IgE production; PAH-DEP can synergize in production of IgE from B cells as well as alter expression of T and B cell surface molecules relevant to IgE production. This project will examine how PAH-DEP modulates defined steps in pathways for IgE production and thereby determine the mechanisms by which PAH-DEP alter the IgE response quantitatively (total amount of IgE protein) and qualitatively (relative amount of the 6 isoforms of epsilon chains [4 secreted and 2 membrane] generated by alternative splicing [described by us]). Specifically we will #1 determine the direct effects of PAH-DEP on NB cell a) surface molecules/receptors relevant to IgE synthesis, b) epsilon mRNAs transcript levels and splicing variants and c) the amount of membrane and secreted IgE isoforms produced. This involves stimulating human B cells through defined stages in IgE production (epsilon germ line transcription, epsilon isotype switch and modulation of productive epsilon mRNA) and defining how PAH- DEP alters these processes and outcomes. We will #2) assess PAH-DEP for the ability to modify the activation/contact signals provided by T cells (and T cell subsets) involved in IgE production. This includes both multicolor flow cytometric phenotypic studies and functional studies of PAH-DEP treated T cells' ability to collaborate in IgE production. #3) The ability to PAH-DEP to alter the production of key cytokines involved in pathways for IgE production (e.g. IL-4, TGFbeta, IL-6, etc.) will be examined at both the protein and MRNA levels. We will extend these studies in vivo by #4a) assessing diesel exhaust particle (DEP) effects on the in vivo IgE antibody response in low and high aromatic hydrocarbon hydrolase activity (Ah activity) mice. These studies will prove whether PAH-DEP is working via the common Ah receptor complex as well as provide for a model to extend studies of kinetics of exposure to PAH-DEP. We will also undertake #4b) in vivo human challenge studies of the topical effects of DEP on the expression of the quantitative and qualitative IgE response in the upper airway. Our studies will provide insight into what may be one of the critical factors affecting the change in allergic airway disease that has occurred this century.