CD14-dependent and independent pathways in lipopolysaccharide-induced activation of a murine B-cell line, CH12.LX

Using a lipopolysaccharide (LPS)-responsive murine B-cell line, CH12.LX, we assessed the possible role of CD14 in LPS-induced activation of B cells. F low cytometric analysis indicated that CH12.LX cells expressed the CD14 mol ecule with a lower intensity than did the macrophage cell line J774.1. A re verse transcription-polymerase chain reaction and Northern blot analysis re vealed low, but significant, levels of CD14 mRNA in CH12.LX cells, whose cD NA was identical to that of the mouse macrophage CD14 gene. After stimulati on with LPS, CH12.LX cells proliferated, accompanied by up-regulations of C D14, transforming growth factor (TGF)-beta and interleukin (IL)-6 mRNA, and increased IgM and IgA secretion. In the absence of serum or with the addit ion of anti-CD14 monoclonal antibodies, however, LPS-stimulation induced ne ither the up-regulation of CD14 and TGF-beta mRNA nor an increase in IgA se cretion. These findings indicate that CD14 expression is not restricted to myeloid cells, but is involved in some cellular activation events of murine B cells elicited by LPS. Furthermore, a CD14-independent pathway may also exist in the LPS-induced activation of B cells that leads to proliferation, IL-6 production and the enhancement of IgM (but not IgA) secretion.