Abstract

How farming protects against allergies People who grow up on dairy farms only rarely develop asthma or allergies. This is probably because as children, they breathe air containing bacterial components, which reduce the overall reactivity of the immune system. Schuijs et al. chronically exposed mice to bacterial endotoxin before they received an allergic stimulus. The protocol indeed protected them from developing an allergic response. Protection relied on a particular enzyme: A20. In humans, a variant of A20 correlates with increased susceptibility to asthma and allergy in children growing up on farms. Science , this issue p. 1106