GM-CSF increases cross-presentation and CD103 expression by mouse CD8⁺ spleen dendritic cells.

Resident CD8(+) DCs perform several functions, including cross-presenting antigen and rapidly engulfing the Gram-positive intracellular pathogen Listeria monocytogenes. Little is known about how these functions of CD8(+) DCs are modulated. Here, we show that granulocyte-macrophage CSF (GM-CSF), a cytokine that exists at low levels at steady state but is elevated during infection and inflammation, enhances cross-presentation and rapid uptake of L. monocytogenes by resident CD8(+) DCs. This previously unrecognized functional enhancement of CD8(+) DCs by GM-CSF was independent of promoting DC survival in vitro. Enhancement of these functions by GM-CSF was also marked by CD103 expression on CD8(+) DCs that was strongly regulated by GM-CSF. Our findings not only identify GM-CSF as a key molecule regulating CD8(+) DC function, but also as a factor responsible for functional heterogeneity of CD8(+) DCs that is at least substantially demarcated by CD103 expression.