IL-25 is a cytokine with considerable T helper type 2 response–promoting properties and is therefore important in the etiology of asthma. In Nature Medicine, Lukacs and colleagues identify a previously unknown IL-25-responsive cell in the lungs that seems to be key in driving disease in a steroid-resistant model of asthma. IL-25 is the main cytokine released in the lungs after sensitization of mice with cockroach allergen. Sensitization also results in the appearance of a non–B cell, non–T cell granulocytic population that expresses the IL-17RB receptor for IL-25. In response to IL-25, these 'T2M' cells become major producers of IL-4 and IL-13, two cytokines critical for the asthma phenotype. The adoptive transfer of T2M cells into otherwise asthma-resistant Il17rb−/− host mice demonstrates that these cells are sufficient to induce disease. This population also seems to be relevant to humans, as the peripheral blood of patients with asthma has a greater abundance of T2M-analogous cells.

Nat. Med. (29 April 2012) doi:10.1038/nm.2735