EFFECT OF LIPOPOLYSACCHARIDE ON MOUSE MAST-CELL INDUCTION BY A SPLENIC CELL-CULTURE SYSTEM

We have previously reported a method of mast cell induction by long term culture of mouse spleen cells without using exogenous mast cell growth factor (Z.-Q. Hu, T. Yoshida, and T. Shimamura, J. Immunol. Methods 149:173, 1992). Supernatants recovered from the long-term cultures contain endogenous interleukin 3 and soluble stem cell factor. These were assessed by the capacity of the recovered supernatants to foster the growth of a mast cell growth factor dependent cell line and by neutralizing antibodies. Besides the soluble factors, cell-to-cell contacts mediated by membrane stem cell factor on splenic stromal cells and c-Kit receptors on mast cells also affect mast cell induction. Different lots of fetal calf serum (FCS) were examined to determine a possible trigger for cytokine production. FCS can be divided into mast cell-inducible and noninducible sera by this process. However, not all FCS lots contain mast cell growth factor. The mast cell-inducible lots contain lipopolysaccharide (LPS) confirmed by a Limulus assay. Polymyxin B can neutralize the mast cell induction activity. Non-mast cell-inducible FCS can be converted to inducible FCS by adding exogenous LPS. The results indicate that LPS as a trigger of cytokine production is responsible for mast cell induction.