Requirement for CD8(+) T cells in the development of airway hyperresponsiveness in a murine model of airway sensitization

To study the role of CD8(+) T cells in allergic sensitization, we examined the effects of in vivo depletion of CD8(+) T cells prior to sensitization on ISE production, immediate type cutaneous hypersensitivity and development of altered airway responsiveness. BALB/c mice were thymectomized and treated with anti-CD8, antibody resulting in depletion of CD8(+) T cells (<1%) in spleen and lymphoid tissues. In these mice, sensitization to ovalbumin (OVA) via the airways still resulted in ISE anti-OVA responses and immediate cutaneous reactions to OVA, but the animals were unable to develop airway hyperresponsiveness, eosinophil infiltration of the lung parenchyma, or IL-5 production in the local lymph nodes of the airway. Transfer of CD8(+) T cells from naive animals during sensitization (on day 8 of the 10-d protocol) fully restored the ability to develop airway hyperresponsiveness and this was accompanied by IL-5 production and eosinophil accumulation in the lung. These data indicate a critical role for CD8(+) T cells in the production of IL-5 and the development of altered airway responsiveness after antigen sensitization through the airways.