Human Peripheral Blood‐Derived Dendritic Cells do not Produce Interleukin 1α, Interleukin 1β, or Interleukin 6

Little is known about the non‐antigen‐specific signals delivered to T cells by dendritic cells (DC). Because several monocyte‐derived factors like interleukins 1α, 1β, and 6 (IL‐1α, IL‐1β, 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‐1α and IL‐6) was studied at a single‐cell level using an immunolabelling technique. The supernatants and cell lysates were studied with ELISA (IL‐1α and IL‐1β). Northern blotting analysis was used to quantitate the mRNA levels. Several approaches were taken to stimulate the production of IL‐1α, IL‐1β, 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‐1α, 1L‐1β, 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‐1α, IL‐1β, 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.