Gene-environment interaction in farming

Farming related health problems, like asthma-like disorders are known since a long time. Most evidence comes from case-series and epidemiological investigations, and more recent studies has shed light on the mechanistic pathways involved. It seems that farmers are more likely to develop a non-immune mediated neutrophilic inflammation of the lungs, ultimately resulting in airway symptoms like wheeze and chronic cough and an accelerated lung function decline. Interestingly, studies in children showed that farmers’ children are less likely to report atopic asthma and hay-fever, than children not living on a farm, but at the same time or more likely to report non-atopic asthma and/or wheeze. This has been confirmed in adult farmer’s or agricultural population studies, and especially linked to endotoxin exposure, a lipopolyssacharide (LPS) present in the outer wall of gram-negative bacteria.  Genetic factors which alter an individual’s susceptibility to farming related exposures have been studied, both in farmers’ children and occupational exposed populations. Several candidate genes have been studied, starting with polymorphisms of genes coding the intracellular domain of toll like receptor 4 (TLR4). Subsequently, polymorphisms of CD14, a receptor protein which binds LPS and transports it to TLR4, and genes involved in the CD14-TLR4-MyD88 dependent pathway have been studied, as well as other TLRgenes like TLR2, and TLR9. More recently, whole genome screening following gene-environment analysis have been studied. In farming, other than TLR genes might be of importance as well, like (alpha)1-antitrypsin. This presentation will present an overview of the body of evidence obtained from these studies especially when considering gene-environment interactions.