Evidence that CD8+ dendritic cells enable the development of gammadelta T cells that modulate airway hyperresponsiveness.

Airway hyperresponsiveness (AHR), a hallmark of asthma and several other diseases, can be modulated by gamma delta T cells. In mice sensitized and challenged with OVA, AHR depends on allergen-specific alpha beta T cells; but V gamma 1(+) gamma delta T cells spontaneously enhance AHR, whereas V gamma 4(+) gamma delta T cells, after being induced by airway challenge, suppress AHR. The activity of these gamma delta T cell modulators is allergen nonspecific, and how they develop is unclear. We now show that CD8 is essential for the development of both the AHR suppressor and enhancer gamma delta T cells, although neither type needs to express CD8 itself. Both cell types encounter CD8-expressing non-T cells in the spleen, and their functional development in an otherwise CD8-negative environment can be restored with transferred spleen cell preparations containing CD8(+) dendritic cells (DCs), but not CD8(+) T cells or CD8-DCs. Our findings suggest that CD8(+) DCs in the lymphoid tissues enable an early step in the development of gamma delta T cells through direct cell contact. DC-expressed CD8 might take part in this interaction.