Generation of monocyte-derived dendritic cells from precursors in rhesus macaque blood

While the dendritic cells (DCs) of mouse and man have been extensively studied, until recently those of non-human primates remained poorly characterized. We present a method for generating large numbers of DCs from precursors in rhesus macaque blood, based on techniques developed for human blood. For 7 days, a T cell-depleted population of mononuclear cells was cultured in 1% human plasma with GM-CSF and IL-4, both to initiate DC differentiation and to inhibit macrophage development. On day 7, 50% of the culture medium was replaced with a monocyte-conditioned medium (MCM), which is required for the final maturation of the DCs into potent stimulators of the allogeneic MLR. Between 0.5 and 1.0 x 10⁶ DCs can be generated from 20 ml of rhesus macaque blood. We compared these cytokine-generated DCs to the adherent macrophages present in the same cultures. Cytokine-generated DCs were considerably more potent at stimulating allogeneic T cells than adherent macrophages. Furthermore, the DCs had a distinct morphology and phenotype, with long processes, high levels of p55, and a characteristic perinuclear collection of intracellular CD68. In contrast, adherent macrophages expressed very low levels of p55, and high diffuse levels of CD68. Macaqae DCs generated by this method may be useful in vaccine development, and for studies of SIV pathogenesis.