Macrophages derived from rat bone marrow were treated with macrophage colony stimulating factor (M-CSF) to obtain a sufficient number of cells for the tumor necrosis factor (TNF-α) assay. The present study has been designed to investigate whether the production of TNF-α, which induces multinucleated giant cell formation, is regulated by polyanions such as lignin derivatives. ELISA for TNF-α showed that the polyanion induced TNF-α production by macrophages. The secretion of TNF-α from the cells reached a maximum at 3-6 h, and then showed a slight decline. Northern blotting of TNF-α mRNA showed that the amount of TNF-α reached a maximum within 1 h of macrophage culture in the presence of a lignin derivative. On the other hand, TNF-α mRNA was undetectable in the control cells. It was concluded that stimuli such as that provided by lignin derivatives increases the amount of TNF-α mRNA, which is then followed by translation of TNF-α.