Interleukin-HP1-related Hybridoma and Plasmacytoma Growth Factors Induced by Lipopolysaccharide in Vivo

Serum of lipopolysaccharide (LPS)-treated mice was found to support the growth of interleukin-HP1 (HP1)-dependent hybridoma and plasmacytoma cell lines. This growth-promoting activity, which was undetectable in normal serum, rose more than 1000-fold within 2 h after i.v. injection of the toxin and disappeared in less than 1 day. It could be traced to a single component, which behaved like HP1 in sodium dodecyl sulfate-polyacrylamide gel electrophoresis and reverse phase high performance liquid chromatography, and was completely inhibited by a rabbit anti-HP1 antiserum. The LPS-induced factor was apparently not of T cell origin, as indicated by the strong activity found in the serum of LPS-treated nude mice. In vitro, LPS also considerably enhanced the production by macrophages of a factor with similar characteristics.