Worming away from allergies

Worms in the gut keep allergies at bay, say Wilson and colleagues on page 1199. Parasitic helminth infections, they show, activate regulatory T (T reg) cells in the gut. These T reg cells are then dispatched to the lungs, where they dampen the immune response to inhaled allergens.

Parasitic worm infections, common among children in tropical and subtropical regions, are associated with decreased responsiveness to allergens. The hygiene hypothesis, which posits that decreased childhood exposure to T helper (Th) 1–inducing microbes (such as bacteria and viruses) increases the risk of developing Th2-driven allergies later in life, might explain this observation. But the allergy-soothing effect of worm infections is unlikely to be due to Th1–Th2 antagonism, as both helminth infections and allergies induce potent Th2 responses.Wilson and colleagues now show that mice infected with...