Occupational endotoxin exposure: Allergic and respiratory health effects and characterization of immunological responses

Abstract

Farmers’ children have fewer allergies than non-farmer’s children. Organic dust exposure and the microbial component of this dust, endotoxin, a cell-wall component of Gram-negative bacteria, is a major factor in the explanation of this protective effect. However, farmers and agricultural workers tend to have more respiratory problems. Previous studies have shown a possible protective effect of endotoxin exposure on the development of allergies, but at the same time there seem to be detrimental effects of (high) endotoxin exposure on respiratory health. This has been shown in cross-sectional studies in which associations between exposure and health effects are determined at one time point. In this thesis, we investigate the association between endotoxin exposure and respiratory health and allergic sensitization in adults in a longitudinal setup over five years. Additionally, we investigated in both mice and men whether certain immune responses are associated with endotoxin exposure. In conclusion, this research shows over a prolonged period of time that endotoxin exposure protects from development of allergies in an occupationally exposed population. This protective effect is also present in mice exposed to organic dust from the same work environments. Furthermore, signs suggest that the protective effect might be specific for people with a typical low immune response in a test where blood is exposed outside the body (ex vivo) to endotoxin. We did not find a clear relationship between endotoxin exposure and respiratory effects.