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  • Title: Cytokine regulation by platelet-activating factor in a human B cell line.
    Author: Smith CS, Parker L, Shearer WT.
    Journal: J Immunol; 1994 Nov 01; 153(9):3997-4005. PubMed ID: 7930608.
    Abstract:
    TNF-alpha is an inflammatory cytokine produced by B cells that also impacts B cell differentiation and Ig secretion. We have investigated the regulation of the TNF-alpha gene in a human B cell line in response to platelet-activating factor (PAF), a potent phospholipid often produced in inflammatory reactions. We report here that PAF increases the RNA levels for the TNF-alpha gene in the human B cell line Ramos. This is mediated by an increase in the transcription rate and a longer half-life of the TNF-alpha transcripts. Induction of the TNF-alpha gene is rapid in these cells and independent of new protein synthesis. Despite increasing RNA for the TNF-alpha gene, PAF increases TNF-alpha protein levels only in the presence of a costimulus, such as PMA. We hypothesize that PAF acts at the transcriptional level to increase TNF-alpha RNA, but a post-transcriptional block acts to regulate protein production. We also report that PAF enhances PMA-induced TNF-alpha production from human peripheral B cells. This increase is maximal at 0.1 microM PAF and is blocked by PAF receptor antagonists. The ability of PAF to modulate cytokine production from human B cells provides further evidence that PAF has a role in B cell biology and suggests it may be important in conditions involving B cell-derived cytokines.
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