Human Peripheral Blood-Derived Dendritic Cells do not Produce Interleukin 1alpha, Interleukin 1beta, or Interleukin 6

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Abstract
Little is known about the non-antigen-specific signals delivered to T cells by dendritic cells (DC). Because several monocyte-derived factors like interleukins 1.alpha., 1.beta., and 6 (IL-1.alpha., IL-1.beta., and IL-6) enhance the T-cell proliferative responses, we studied the production of the above-mentioned cytokines by DC separated from human peripheral blood. The intracellular expression of the proteins (IL-1.alpha. and IL-6) was studied at a single-cell level using an immunolabelling technique. The supernatants and cell lysates were studied with ELISA (IL-1.alpha. and IL-1.beta.). Northern blotting analysis was used to quantitate the mRNA levels. Several approaches were taken to stimulate the production of IL-1.alpha., IL-1.beta., and IL-6 by DC. These included the incubation of the DC in the presence of either LPS, rIL-1, or monoclonal anti-HLA-DR antibody, or the stimulation of cells with resting allogeneic T cells. None of the stimuli was able to induce the production of IL-1.alpha., IL-1.beta., or IL-6 by DC, whereas LPS-stimulated monocytes were strong producers of these mentioned cytokines and expressed the respective mRNA. Thus we concluded that IL-1.alpha., IL-1.beta., and IL-6 are primarily monocyte-derived factors and that these factors are not needed or produced during the activation of resting T cells by DC.