Selective interaction between lymphocytes and lipid A subunits in lipopolysaccharide macromolecular aggregates.

The interaction between bacterial lipopolysaccharides (LPS) and murine spleen cells was examined. The results indicate that lipid A-rich subunits, contained within the heterogeneous LPS macromolecule, associated selectively with spleen cells. In the LPS not associated with spleen cells, the relative amounts of lipid A-rich subunits were reduced; however, this reduction was not of a sufficient magnitude to be reflected in the stimulation of B cells. By constructing hybrid LPS macromolecules with various amounts of lipid A-rich subunits it was documented that mitogenic activity of B cells was relatively refractory to lipid A subunit composition. Furthermore, the presence of polysaccharide-rich subunits regulated downward the expression of lipid A-dependent activity.