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

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Abstract
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.