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Different Potentials of γδ T Cell Subsets in Regulating Airway Responsiveness: Vγ1+ Cells, but Not Vγ4+ Cells, Promote Airway Hyperreactivity, Th2 Cytokines, and Airway Inflammation1

Allergic airway inflammation and hyperreactivity are modulated by γδ T cells, but different experimental parameters can influence the effects observed. For example, in sensitized C57BL/6 and BALB/c mice, transient depletion of all TCR-δ+ cells just before airway challenge resulted in airway hyperresponsiveness (AHR), but caused hyporesponsiveness when initiated before i.p. sensitization. Vγ4+ γδ T cells strongly suppressed AHR; their depletion relieved suppression when initiated before challenge, but not before sensitization, and they suppressed AHR when transferred before challenge into sensitized TCR-Vγ4−/−/6−/− mice. In contrast, Vγ1+ γδ T cells enhanced AHR and airway inflammation. In normal mice (C57BL/6 and BALB/c), enhancement of AHR was abrogated only when these cells were depleted before sensitization, but not before challenge, and with regard to airway inflammation, this effect was limited to C57BL/6 mice. However, Vγ1+ γδ T cells enhanced AHR when transferred before challenge into sensitized B6.TCR-δ−/− mice. In this study Vγ1+ cells also increased levels of Th2 cytokines in the airways and, to a lesser extent, lung eosinophil numbers. Thus, Vγ4+ cells suppress AHR, and Vγ1+ cells enhance AHR and airway inflammation under defined experimental conditions. These findings show how γδ T cells can be both inhibitors and enhancers of AHR and airway inflammation, and they provide further support for the hypothesis that TCR expression and function cosegregate in γδ T cells.