Modulation of asthma by endotoxin.

Asthma is a common inflammatory disease triggered by both allergic and non-allergic stimuli. The most common risk factor in the development of asthma is induction of IgE against indoor allergens and imbalance in the T-helper type 1 (Th1) and Th2 with skewing towards Th2 response. Interplay of genetic and environmental factors is involved in induction and propagation of asthma. Endotoxin is a common environmental pollutant and elicits a Th1 response. The amount of endotoxin varies with several factors but of significant interest has been the role of pets. Endotoxin not only protects against the development of asthma but also enhances an already established inflammation. The difference of outcomes is likely not only due to the time and dose of exposure but also as we discuss the variable interaction of genes with environment. We focus on studies since 2001 that have explored the role of endotoxin in asthma and the gene-environment interactions of the endotoxin effect.