Sequential induction of phospholipid methylation and serine esterase activation in a B cell differentiation factor (BCDF)-stimulated human B cell line

The incubation of CESS cells with BCDF induced phospholipid methylation, i.e., ³H-methyl incorporation into phosphatidylcholine and phosphatidyl-N-monomethylethanolamine, within 15 to 30 min. A threefold increase of ³H-DFP-binding was also observed in BCDF-stimulated CESS cells 2 hr after stimulation, showing the activation of serine esterase after phospholipid methylation. The inhibitors of methyltransferase, SIBA, adenosine, or HEH showed a dose-dependent inhibitory effect not only on phospholipid methylation but also on serine esterase activation and on BCDF-induced IgG production; DFP inhibited IgG production but not phospholipid methylation. The treatment of cells with DFP in the presence of SIBA abrogated the irreversible inhibitory effect of DFP on IgG production. These results showed that BCDF stimulation induced phospholipid methylation that set the stage for serine esterase activation and IgG induction.