CCR5 provides a signal for microbial induced production of IL-12 by CD8 alpha(+) dendritic cells

The activation of dendritic cells (DC) to produce interleukin 12 (IL-12) is thought to be a key step in the initiation of cell-mediated immunity to in tracellular pathogens. Here we show that ligation of the C-C chemokine rece ptor (CCR) 5 can provide a major signal for the induction of IL-12 synthesi s by the CD8 alpha(+) subset of DC and that this pathway is important in es tablishing interferon gamma-dependent resistance to the protozoan parasite Toxoplasma gondii. These findings support the concept that the early induct ion of chemokines by invading pathogens is a critical step not only for the recruitment of DC but also for the determination of their subsequent immun ologic function.