CD8+ T cells regulate immune responses in a murine model of allergen‐induced sensitization and airway inflammation

The role of CD8+ T cells in the development of allergic airway disease is controversial. On the one hand, CD8+ T cells are known to inhibit the development of airway hyperreactivity (AHR) in murine models of asthma. In humans, IL-10-producing CD8+ T cells were shown to act as regulatory cells, inhibiting both proliferation and cytokine secretion of T cells. On the other hand, CD8+ T cells can promote IL-5-mediated eosinophilic airway inflammation and the development of AHR in animal models. To examine this, we investigated the role of CD8+ T cells during the induction of allergen-induced AHR and demonstrated a protective effect of CD8+ T cells. Depletion of CD8+ T cells prior to the immunization led to increased Th2 responses and increased allergic airway disease. However, after development of AHR, CD8+ T cells that infiltrated the lungs secreted high levels of IL-4, IL-5 and IL-10, but little IFN-γ, whereas CD8+ T cells in the peribronchial lymph nodes or spleen produced high levels of IFN-γ, but little or no Th2 cytokines. These data demonstrate protective effects of CD8+T cells against the induction of immune responses and show a functional diversity of CD8+ T cells in different compartments of sensitized mice.