LIPOPOLYSACCHARIDE-DEPENDENT INDUCTION OF IL-10 RECEPTOR EXPRESSION ON MURINE FIBROBLASTS

Although various biologic activities of IL-10 have been identified, little is known about IL-10's molecular mechanism of action. Herein we report the characterization of IL-10R on different murine cell lines and demonstrate the LPS inducibility of this protein. With the use of purified recombinant murine IL-10 and labeled IL-10-specific mAb, IL-10Rs were detected by flow cytometry. Radioligand binding analyses showed that RAW264.7 cells expressed 238 +/- 87 receptors per cell and bound ligand with a single affinity of 8.3 +/- 2.4 X 10(9) M(-1). Similar studies documented IL-10R expression on murine B cells (CH27) and CD4(+) Th1 cells but not murine Th2 cells, L929 or WA-17 fibroblasts, or fibrosarcoma cells. Exposure of fibroblasts to LPS-induced cellular IL-10 binding activity in a dose- and time-dependent manner. Radioligand binding analyses performed on LPS-treated fibroblasts showed cellular expression of 325 +/- 59 IL-10 binding sites and a binding affinity of K-a = 7.5 +/- 2.5 X 10(8) M(-1). RT-PCR analysis confirmed the induction of the IL-10R. Functional analyses of IL-10R-expressing cells revealed that IL-10 activated a cellular transcription factor in RAW264.7 cells that bound a DNA probe containing the IFN-gamma response region from the Fc gamma RI gene. In contrast, IL-10 did not induce gamma response region binding activity in L929 fibroblasts either treated with LPS or transfected with the murine IL-10R cDNA. These results thus indicate that cellular responses to IL-10 may be influenced by both the external environment and the presence of additional signaling components within the cell.