A new 'antigen-presenting' function for specialized immune cells that allows them to initiate allergy or mount immune responses against parasites is reported online in three papers in Nature Immunology. The research highlights the cells, known as basophils, as therapeutic targets for short-circuiting allergic responses.

Basophils are an immune cell that releases chemical mediators that can trigger the wheezing, itching and other symptoms that accompany allergic reactions. Groups led by David Artis, Kenji Nakanishi and Ruslan Medzhitov show basophils act as the first responders that present antigen to nave T cells. These 'primed' T cells instruct the immune system to secrete interleukin 4 and immunoglobulin E, which help to repel worms and other parasites, but also underlie allergic responses.

Previously, basophils were thought to act after individuals had become 'sensitized' through previous contact with allergen or worm exposure. The new work reveals how these cells both initiate and amplify allergic reactions, such that once initiated by contact with allergen they become difficult to control, as any allergy sufferer can attest.

This research rules out earlier assumptions that dendritic cells, an important antigen-presenting cell for viral and bacterial infections, initiate the allergic response.