The leukotriene B4 receptor (BLT1) is required for effector CD8⁺ T cell-mediated, mast cell-dependent airway hyperresponsiveness

Studies in both humans and rodents have suggested that CD8⁺ T cells contribute to the development of airway hyperresponsiveness (AHR) and that leukotriene B4 (LTB4) is involved in the chemotaxis of effector CD8⁺ T cells (T_EFF) to the lung by virtue of their expression of BLT1, the receptor for LTB4. In the present study, we used a mast cell-CD8-dependent model of AHR to further define the role of BLT1 in CD8⁺ T cell-mediated AHR. C57BL/6^+/+ and CD8-deficient (CD8^-/-) mice were passively sensitized with anti-OVA IgE and exposed to OVA via the airways. Following passive sensitization and allergen exposure, C57BL/6 ^+/+ mice developed altered airway function, whereas passively sensitized and allergen-exposed CD8^-/- mice failed to do so. CD8 ^-/- mice reconstituted with CD8⁺ T_EFF developed AHR in response to challenge. In contrast, CD8^-/- mice reconstituted with BLT1-deficient effector CD8⁺ T cells did not develop AHR. The induction of increased airway responsiveness following transfer of CD8 ⁺ T_EFF or in wild-type mice could be blocked by administration of an LTB4 receptor antagonist confirming the role of BLT1 in CD8⁺ T cell-mediated AHR. Together, these data define the important role for mast cells and the LTB4-BLT1 pathway in the development of CD8 ⁺ T cell-mediated allergic responses in the lung.