Expression of lymphocyte cell surface markers in workers exposed to different respiratory hazards: biomarkers of occupational respiratory disease?

This study was designed to evaluate the potential of flow cytometry to measure biomarkers of airways inflammation in the peripheral blood of two cohorts of workers reporting work-related respiratory symptoms, who were exposed to different respiratory hazards. Nine bakers exposed to wheat flour and 10 glass bottle manufacturers exposed to a range of irritant chemicals were selected for study. Phenotypic and inducible cell surface markers were measured by flow cytometry. Results were compared with a control population of 58 volunteers reporting no respiratory problems. The bakers showed a significant increase above control values for cell types associated with inflammation; in particular CD3 + CD4+ cells (p < 0.005) and CD4 + CD25 + cells (p < 0.01). In contrast, the workers reporting work-related respiratory symptoms who were exposed to a range of irritant chemicals showed a different pattern of cell surface lymphocyte markers, with a significant decrease in the total T-cell population (p < 0.05). Comparison of results from a subset of smoking controls with the population of bakers (who were all heavy smokers) confirmed that the increase in CD3 + CD4+ cells and CD4 + CD25+ cells could not be ascribed to the effects of smoking alone, We have shown activation of helper T-cells in the peripheral blood of bakers reporting work-related respiratory symptoms consistent with the changes observed in mild to severe asthmatics. However, workers with similar symptoms who were exposed to irritant chemicals did not show this pattern of phenotypic or inducible cell surface markers, reflecting an absence of airways inflammation in these individuals, Our results suggest that flow cytometry may be of use as an objective test for detecting workers with airways inflammation to allow the identification of workers at risk of developing occupational asthma.