Influence of endotoxin on production of leucocyte migration inhibition factor. Part I

Commercial reagents are often contaminated with endotoxins in concentrations which may affect biological immunoassays. The endotoxin lipopolysaccharide from E. coli 026:B6, at concentrations at and above 5 X 10(-9) g/ml induces mononuclear cells to produce the lymphokine leucocyte migration inhibition factor (LIF). However, lipopolysaccharide at concentrations at or above 5 X 10(-8) inhibit leucocyte migration making it impossible to measure the effect of LIF. Standardization of endotoxin content during production and assay of LIF is needed, in order to reduce the variability of the results.