Cutting edge: Granulocyte-macrophage colony-stimulating factor is the major CD8 + T cell-derived licensing factor for dendritic cell activation

Abstract

During priming, CD8 + T lymphocytes can induce robust maturation of dendritic cells (DCs) in a CD40-independent manner by secreting licensing factor(s). In this study, we isolate this so-far elusive licensing factor and identify it, surprisingly, as GM-CSF. This provides a new face for an old factor with a well-known supporting role in DC development and recruitment. Signaling through the GM-CSFR in ex vivo-purified DCs upregulated the expression of costimulatory molecules more efficiently than did any tested TLR agonist and provided a positive feedback loop in the stimulation of CD8 + T cell proliferation. Combined with a variety of microbial stimuli, GM-CSF supports the formation of potent "effector" DCs capable of secreting a variety of proinflammatory cytokines that guide the differentiation of T cells during the immune response. Copyright © 2010 by The American Association of Immunologists, Inc.