Monoclonal non-specific suppressor factor (MNSF) inhibits the IL4 secretion by bone marrow-derived mast cell (BMMC)

We investigated whether monoclonal non-specific suppressor factor (MNSF) has an effect on the IL4 secretion by BMMC sensitized with anti-DNP IgE monoclonal antibody. The sensitized BMMC showed a maximum increase of IL4 secretion at 10 ng/ml antigen activation. When MNSF (10 U) was added, it remarkably suppressed the IL4 secretion (82 +/- 3%). MNSF also suppressed the IL4 secretion by the mast cell line, CFTL-15, but not CFTL-12. Northern blot analysis showed that, when the same amounts of MNSF were added, IL4 mRNA expression was decreased, suggesting that the suppression results from the inhibition of a transcript.