Plasmodium falciparum Activates CD16(+) Dendritic Cells to Produce Tumor Necrosis Factor and Interleukin-10 in Subpatent Malaria

BACKGROUND: The malaria causing parasite Plasmodium subverts host immune responses by several strategies including the modulation of dendritic cells (DCs). METHODS: In this study, we show that Plasmodium falciparum skewed CD16(+) DC cytokine responses towards interleukin (IL)-10 production in vitro, distinct to the cytokine profile induced by Toll-like receptor ligation. To determine CD16(+) DC responsiveness in vivo, we assessed their function after induced P falciparum infection in malaria-naive volunteers. RESULTS: CD16(+) DCs underwent distinctive activation, with increased expression of maturation markers human leukocyte antigen (HLA)-DR and CD86, enhanced tumor necrosis factor (TNF) production, and coproduction of TNF/IL-10. In vitro restimulation with P falciparum further increased IL-10 production. In contrast, during naturally acquired malaria episode, CD16(+) DCs showed diminished maturation, suggesting increased parasite burden and previous exposure influence DC subset function. CONCLUSIONS: These findings identify CD16(+) DCs as the only DC subset activated during primary blood-stage human Plasmodium infection. As dual cytokine producers, CD16(+) DCs contribute to inflammatory as well as regulatory innate immune processes.