Bacterial lipopolysaccharide mediates the loss of CD4 from the surface of purified peripheral blood monocytes.

In this study we have looked at the effect of lipopolysaccharide (LPS) on the surface antigen expression of cultured monocytes. Monocytes were purified from peripheral blood mononuclear cells (PBMC) and cultured in the presence or absence of LPS. The cultured cells were then stained with anti-MO3, anti-IL-2R and anti-CD4 MoAbs. We have shown that freshly isolated monocytes are IL-2R- and MO3-negative and express CD4 in low density. After overnight culture, without LPS, the expression of these surface markers remained relatively unchanged. However, in the presence of LPS (1 microgram/ml) CD4 expression was reduced to undetectable levels while the expression of IL-2R and MO3 was induced to maximal density. This effect of LPS on monocyte surface antigen expression was demonstrated with LPS preparations from Escherichia coli, Salmonella typhi and Vibrio cholerae. Surface antigen expression after 7 days culture in medium supplemented with non-heat-inactivated serum was essentially as seen after overnight culture, with the exception that LPS-induced IL-2R expression was transient. The ability to prepare monocytes that maintained surface CD4 expression after overnight culture was donor dependent.