Dendritic cells (DCs) are sentinels of the immune system that uniquely prime naive cells and initiate adaptive immune responses. CD1c (BDCA-1) myeloid DCs (CD1c+ mDCs) highly express HLA-DR, have a broad Toll-like receptor (TLR) repertoire, and secrete immune modulatory cytokines. To better understand immune responses to malaria, CD1c+ mDC maturation and cytokine production were examined in healthy volunteers before and after experimental intravenous Plasmodium falciparum infection with 150- or 1,800-parasite-infected red blood cells (pRBCs). After either dose, CD1c+ mDCs significantly reduced HLA-DR expression in prepatent infections. Circulating CD1c+ mDCs did not upregulate HLA-DR after pRBC or TLR ligand stimulation and exhibited reduced CD86 expression. At peak parasitemia, CD1c+ mDCs produced significantly more tumor necrosis factor (TNF), whereas interleukin-12 (IL-12) production was unchanged. Interestingly, only the 1,800-pRBC dose caused a reduction in the circulating CD1c+ mDC count with evidence of apoptosis. The 1,800-pRBC dose produced no change in T cell IFN-? or IL-2 production at peak parasitemia or at 3 weeks posttreatment. Overall, CD1c+ mDCs are compromised by P. falciparum exposure, with impaired HLA-DR and CD86 expression, and have an increased capacity for TNF but not IL-12 production. A first prepatent P. falciparum infection is sufficient to modulate CD1c+ mDC responsiveness, likely contributing to hampered effector T cell cytokine responses and assisting parasite immune evasion. � 2016, American Society for Microbiology. All Rights Reserved.
Loughland, J. R., Minigo, G., Burel, J., Tipping, PE., Piera, K., Amante, F., Engwerda, C., GOOD, M., DOOLAN, D., Anstey, N., McCarthy, J., & Woodberry, T. (2016). Profoundly reduced CD1c+ myeloid dendritic cell HLA-DR and CD86 expression and increased tumor necrosis factor production in experimental human bloodstage malaria infection. Infection and Immunity, 84(5), 1403-1412. https://doi.org/10.1128/IAI.01522-15