Selective association of lipid-rich R-like lipopolysaccharide subunits with murine spleen cells.

SDS-PAGE was used to analyze the subunit composition of 125I-lipopolysaccharide (LPS) in the cell-associated and supernatant fractions of murine spleen cells after culture with radiolabeled LPS from the smooth strain of E. coli O55:B5. Quantitative estimates from densitometric scans of autoradiographs indicated that certain R-like subunits were selectively enriched in cell-associated fractions by a factor of 2.8 as compared to native O55 LPS. Coincident with this selective enrichment was a 57% decrease in these subunits in supernatant fractions. In contrast, the level of polysaccharide-containing subunits in cell-associated fractions was equivalent to or less than the corresponding subunit in native LPS. LPS bound at 37 degrees C was capable of eliciting a significant B-lymphocyte proliferative response in responder spleen cells. However, this selective binding of lipid-rich R-like subunits to splenocytes is insufficient, by itself, to initiate a triggering event since it is both quantitatively and qualititatively indistinguishable in lymphoid cells from the LPS responder (C3HeB/FeJ) mouse and the LPS non-responder (C3H/HeJ) mouse.