title: Exposure-response relationships for inhalant wheat allergen exposure and asthma.
abstract: BACKGROUND
  A few studies have investigated exposure-response relationships for sensitisation to wheat, work-related symptoms and wheat allergen exposure. IgG4 is suggested to protect against the development of allergic sensitisation. The main aim of this current study was to explore the nature of exposure-response relationships for a range of clinically relevant endpoints among bakery workers, and to investigate the role of IgG4 in these relationships.
  
  
  METHODS
  A cross-sectional study of 517 supermarket bakery workers in 31 bakeries used a questionnaire, serum-specific IgE and IgG4 to wheat, and methacholine challenge testing. Exposure models were developed previously using job, bakery size, tasks and specific ingredients used. These models were used to predict average personal exposure to wheat allergens.
  
  
  RESULTS
  The exposure-response relationships for average exposure followed a linear relationship for sensitisation, but a bell-shaped curve for allergic symptoms and probable occupational asthma, increasing up to 10-15 µg/m(3) wheat allergen concentration after which they plateau off and decrease at higher exposure concentrations. This relationship was modified by atopic status. IgG4 levels were strongly exposure related: a clear increase in prevalence of higher IgG4 with increase in wheat allergen exposure was observed among those sensitised and non-sensitised to wheat, with IgG4 even more strongly associated with exposure than IgE to wheat.
  
  
  CONCLUSIONS
  The bell-shaped exposure-response relationship in the current study is consistent with the findings of previous studies. IgG4 showed no protective effect for sensitisation, confirming the findings of previous studies, suggesting that the pattern is probably related to a healthy worker effect.
authors.affiliation: Faculty of Applied Sciences, Department of Environmental and Occupational Studies, Cape Peninsula University of Technology, Cape Town, Western Cape, South Africa Centre for Environmental and Occupational Health Research, School of Public Health and Family Medicine, University of Cape Town, Cape Town, Western Cape, South Africa.
authors.forename: R
authors.initials: R
authors.lastname: Baatjies
authors.affiliation: Division of Environmental Epidemiology, Institute for Risk Assessment Sciences, Utrecht University, Utrecht, The Netherlands.
authors.forename: T
authors.initials: T
authors.lastname: Meijster
authors.affiliation: Division of Environmental Epidemiology, Institute for Risk Assessment Sciences, Utrecht University, Utrecht, The Netherlands.
authors.forename: D
authors.initials: D
authors.lastname: Heederik
authors.affiliation: Centre for Environmental and Occupational Health Research, School of Public Health and Family Medicine, University of Cape Town, Cape Town, Western Cape, South Africa.
authors.forename: M F
authors.initials: MF
authors.lastname: Jeebhay
mesh_terms: D000328:Adult; D000395:Air Pollutants, Occupational / Q000032:analysis / Q000633:toxicity*; D000485:Allergens / Q000009:adverse effects / Q000276:immunology; D059366:Asthma, Occupational / Q000453:epidemiology / Q000209:etiology* / Q000276:immunology; D001939:Bread; D001985:Bronchial Provocation Tests; D003430:Cross-Sectional Studies; D004391:Dust / Q000032:analysis; D005260:Female; D005525:Food-Processing Industry / Q000706:statistics & numerical data; D006801:Humans; D007073:Immunoglobulin E / Q000276:immunology; D007074:Immunoglobulin G / Q000276:immunology; D008297:Male; D016210:Methacholine Chloride; D008875:Middle Aged; D016273:Occupational Exposure / Q000032:analysis*; D015995:Prevalence; D012882:Skin Tests; D013019:South Africa / Q000453:epidemiology; D011795:Surveys and Questionnaires; D014908:Triticum / Q000633:toxicity*; D055815:Young Adult
chemical_list: D000395:Air Pollutants, Occupational; D000485:Allergens; D004391:Dust; D007074:Immunoglobulin G; D016210:Methacholine Chloride; D007073:Immunoglobulin E