Natural Helper Cells Hinder, Too

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Science  10 Jun 2011:
Vol. 332, Issue 6035, pp. 1242
DOI: 10.1126/science.332.6035.1242-b

Viral infections in people with asthma can be particularly bad, because these patients are more prone to develop airway hyperreactivity (AHR) and inflammation, which can lead to substantial morbidity and even death. AHR is also seen in allergic asthma, but conventional therapies used for this disease are often not effective against virus-induced AHR, which suggests different underlying mechanisms of disease development and pathology. Chang et al. sought to determine the cellular and molecular mechanisms that drive AHR in response to viral infection by using mice infected with influenza virus. Infected mice rapidly developed AHR and inflammation that, instead of being dependent on the classical T helper type 2 cytokines typically associated with allergic asthma and AHR, were dependent on interleukin-33 (IL-33). Also unlike allergic asthma and AHR, influenza-induced AHR did not depend on the adaptive immune response. This led the authors to test the role of natural helper cells, an IL-33–secreting, newly described immune cell type that promotes immunity to intestinal helminth infections. Indeed, depletion of natural helper cells blocked the development of AHR in influenza-infected mice, and transfer of these cells to IL-33–deficient, influenza-infected mice restored AHR. Although these results await confirmation in humans, they suggest that, like other immune cell subsets, natural helper cells can have both protective and pathological effects.

Nat. Immunol. 12, 10.1038/ni.2045 (2011).

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