Cell-specific differences in the regulation of IL-6 expression by PMA

We have studied the regulation of IL-6 expression in human blood monocytes and lymphocytes. LPS and IFN-gamma induced IL-6 gene expression with a similar qualitative profile in both cell types. Treatment of monocytes and lymphocytes with PMA resulted, instead, in different effects: monocytes accumulated IL-6 and its message, while lymphocytes were inhibited either in the absence or the presence of LPS and IFN-gamma. These results suggest that the signal transduction pathways triggered by LPS and IFN-gamma are similar in both cell types, while PMA may activate a tissue-specific pathway which leads to opposite responses.