Leukotriene B4 receptor-1 is essential for allergen-mediated recruitment of CD8⁺ T cells and airway hyperresponsiveness

Recent studies in both human and rodents have indicated that in addition to CD4⁺ T cells, CD8⁺ T cells play an important role in allergic inflammation. We previously demonstrated that allergen-sensitized and -challenged CD8-deficient (CD8^-/-) mice develop significantly lower airway hyperresponsiveness (AHR), eosinophilic inflammation, and IL-13 levels in bronchoalveolar lavage fluid compared with wild-type mice, and that all these responses were restored by adoptive transfer of in vivo-primed CD8⁺ T cells or in vitro-generated effector CD8⁺ T cells (T_EFF). Recently, leukotriene B4 and its high affinity receptor, BLT1, have been shown to mediate in vitro-generated T_EFF recruitment into inflamed tissues. In this study we investigated whether BLT1 is essential for the development of CD8⁺ T cell-mediated allergic AHR and inflammation. Adoptive transfer of in vivo-primed BLT1^+/+, but not BLT1^-/-, CD8 ⁺ T cells into sensitized and challenged CD8^-/- mice restored AHR, eosinophilic inflammation, and IL-13 levels. Moreover, when adoptively transferred into sensitized CD8^-/- mice, in vitro-generated BLT1^+/+, but not BLT1^-/-, T_EFF accumulated in the lung and mediated these altered airway responses to allergen challenge. These data are the first to show both a functional and an essential role for BLT1 in allergen-mediated CD8⁺ T_EFF recruitment into the lung and development of AHR and airway inflammation.