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Occupational lung disease

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S Thomas, S Gomez Olles, J Harris, H Jeal, P Cullinan, M Jones. Imperial College, London, UK

Introduction: There is a considerable body of evidence relating the incidence of occupational asthma to the intensity of allergen exposure in the workplace. For most allergens the exposure response for specific sensitisation and symptoms is linear but for some it is more complex. For example, at highest exposure to rat urinary allergens, there is an attenuation in sensitisation and symptoms with an associated increase in specific IgG4 antibodies, which has been described as a modified Th2 response. These specific IgG4 antibodies have previously been shown to be functionally protective. In bakery workers, exposed to varying concentrations of flour allergen, we have demonstrated a linear exposure response for sensitisation and symptoms but the role of specific IgG4 antibodies are unknown.

Aims: To measure levels of flour-specific IgG4 antibodies in 211 bakery workers and determine how these related to the exposure response.

Methods: A cross-sectional study of 239 workers from in-store bakeries across the UK was carried out. Flour-specific IgG4 antibodies were measured in 211 (88.3%) participants using an optimised ELISA technique.

Results: The frequency of individuals producing high flour IgG4 increased with increasing exposure except at maximum exposure whereby the frequency was decreased. There was a modified Th2-like response seen in a category of workers that was likely to have had the highest cumulative exposure throughout their career (see fig). This modified Th2-like response seen in these workers consisted of having low levels of flour-specific IgE and high levels of flour-specific IgG4 with an associated decrease in symptoms.

Conclusions: The relationship between flour-specific IgG4 antibodies and exposure in bakery workers is complex. Flour-specific IgG4 antibodies do not reflect exposure in the bakery workers in this …

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