Cereal-induced occupational asthma

Tolerance mechanisms in response to antigens responsible for baker's asthma in different exposed people

BACKGROUND

Baker's asthma is among the most common occupational disease. The risk factors and immune features that may be important as predictors of tolerance or development of the disease are not completely understood.

OBJECTIVE

To study the evolution over time of antigenic reactivity on baker's asthma in Spain and in France, in order to find differences in their allergenic response and evidence of protective or risks mechanisms against this disease.

METHODS

Two groups of subjects were randomly selected. A group of bakers with asthma from Spain and a second group from France whose blood was taken 30 years ago: bakers with asthma, bakers without occupational respiratory allergy, and wives and children living close to the bakery. In all subjects skin tests were carried out with cereals, insects and the most common allergens in their area. Specific IgE, IgG(4) and IL 10 measurement were also determined.

RESULTS

Spanish patients were mainly sensitized to cereal allergens and presented higher levels of IgE (p < 0.001). French patients are more often sensitised to insects than the Spanish ones: 5.26% versus 80% (p < 0.005). Symptom free or without aggravation at work subjects have higher specific IgG(4) and IL 10 levels than the others (p < 0.01).

CONCLUSIONS

Antigens implicated in baker's asthma may change with time. The presence of higher levels of IgG(4), IL10 and diversity of sources of sensitisation in French patients may have helped them to develop a kind of natural hyposensitization.

Exposure-response relations for self reported asthma and rhinitis in bakers

OBJECTIVES

To explore relations between two estimates of exposure to inhalable flour dust, and the incidence rates (IRs) of asthma and rhinitis in bakers.

METHODS

This was a retrospective cohort study among 2923 bakers. A posted questionnaire registered the disease and work history. For every year, each baker was assigned an estimate of the exposure concentration to inhalable flour dust derived from reported job-tasks and dust measurements. Exposure at onset of disease was expressed as current dust exposure concentration, and as cumulative dose of exposure to dust. A multiple Poisson regression analysis assessed the impacts of the exposure estimates on the IRs of asthma and rhinitis.

RESULTS

IRs of asthma and rhinitis increased by dust concentration at onset of disease. The IR of asthma for the bakers with highest exposure (dough makers) was 7. 3/1000 person-years in men and 6.5 in women and for rhinitis 43.4 and 38.5, respectively. There was a significant association between the dust concentration at onset of disease and the risk for asthma or rhinitis, but not of the cumulative exposure.

CONCLUSION

The risk of asthma seemed to be increased at inhalable dust concentrations >/=3 mg/m(3) (dough making or bread forming), whereas the risk of rhinitis was increased at all concentrations >/=1 mg/m(3), indicating an increased risk in all bakery job-tasks. The risks seemed to be less dependent on the cumulative exposure dust than the inhalable dust concentrations.

Identification and characterization of wheat grain albumin/globulin allergens

Bakers' asthma, an immediate-type allergic response to the inhalation of cereal flours, is an important occupational disease among workers of the baking and milling industries, and the salt-soluble proteins of wheat and rye flour dust are considered the most relevant allergens. In order to identify and characterize the major IgE-binding proteins, the polypeptide composition of the albumin/globulin protein fraction obtained from different cultivars was analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), and high-resolution two-dimensional polyacrylamide gel electrophoresis with immobilized pH gradients in the first dimension (IPG-Dalt), followed by immunoblotting with sera from asthmatic bakers. Relevant allergens were isolated by micropreparative IPG-Dalt and blotting onto polyvinylidenedifluoride membranes and identified by amino acid composition analysis or N-terminal amino acid sequence analysis. SDS-PAGE, IPG-Dalt, and immunoblotting demonstrated that the sera of the bakers allergic to flour contained IgE antibodies which bound to numerous albumin/globulin polypeptides in the 70, 55, 35, 26-28, and 14-18 kDa areas. More detailed investigations using IPG-Dalt revealed cultivar-specific differences in IgE-binding. It was also demonstrated that the majority of the allergens were not single polypeptide spots, but consisted of up to ten isoforms of similar molecular mass but different isoelectric points. Amino acid composition analysis and N-terminal amino acid sequence analysis, which were performed for nine allergens located in the 14-18, 26-28, and 35 kDa areas, revealed homologies to amylase/protease inhibitors, acyl-CoA oxidase and fructose-bisphosphate-aldolase from wheat, barley, maize, and rice, respectively.