Natural Killer T Cells Found in Lungs of Asthmatics

CD4+ cells in asthma patients are natural killer T cells, which may affect treatment

WEDNESDAY, March 15 (HealthDay News) -- The CD4+ cells that are found in large amounts in the lungs of asthma patients are actually natural killer T cells, suggesting that they may play a pathogenic role in the disease, researchers report in the March 16 issue of the New England Journal of Medicine.

Dale T. Umetsu, M.D., Ph.D., of Harvard Medical School in Boston, and colleagues assessed the T cells in the lungs and peripheral blood of 14 patients with asthma, six normal controls and five patients with sarcoidosis, the respiratory inflammatory disease characterized by large numbers of CD4+ type 1 helper (Th1) cells in the lungs.

Sixty percent of the CD4+CD3+ cells found in the lungs of patients with asthma were actually a subset of natural killer T cells that expressed an invariant T cell receptor and produced type 2 helper cytokines rather than conventional class II MHC-restricted CD4+ T cells. In contrast, the researchers found that the CD4+ T cells found in patients with sarcoidosis were conventional CD4+CD3+ T cells.

"Together with studies in mice indicating a requirement for natural killer T cells in the development of allergen-induced airway hyperreactivity, our results strongly suggest that CD4+ natural killer T cells play a prominent pathogenic role in human asthma," Umetsu and colleagues conclude.

In an accompanying editorial, A. Barry Kay, M.D., Ph.D., of Imperial College London, writes that the findings "may have far-reaching consequences for patient care."

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