Down-modulation of L-selectin by lipopolysaccharide is not required for lipopolysaccharide-induced expression of CD14 in mouse bone marrow granulocytes

We established in previous studies that a constitutive lipopolysaccharide ( LPS) receptor of low affinity is present on mouse bone marrow granulocytes (BMG), This yet-unidentified receptor is involved in the LPS-induced expres sion of a second LPS receptor, CD14. Because it has been claimed that L-sel ectin (CD62L) is a low-affinity LPS receptor in mature granulocytes (polymo rphonuclear leukocytes), it may be asked whether this molecule could be the constitutive LPS receptor in BMG. We show in this study that L-selectin is constitutively present on BMG and is down-regulated after exposure of the cells to LPS. A phorbol ester induced a down-regulation of CD62L and blocke d the LPS-induced expression of CD14. However, a metalloproteinase inhibito r (BB-3103) blocked the former but not the latter effect of PR LA. We also observed an absence of cross-reactivity between LPS and a CD62L ligand (fuc oidan) in binding studies with radiolabeled derivatives of the two agents, Furthermore, BMG from L-selectin-deficient mice expressed normal levels of CD14 in response to LPS. Taken together, these results demonstrate that in BMG, L-selectin is not the constitutive LPS receptor required for the LPS-i nduced expression of CD14.