The lipid A region of lipopolysaccharides from Rhizobiaceae activates bonemarrow granulocytes from lipopolysaccharide-hyporesponsive C3H/HeJ andC57BL/10ScCr mice

We established in previous studies that the binding of Salmonella lipopolys accharide (LPS) to constitutive receptors of low affinity triggers the expr ession of the inducible LPS-binding molecule CD14 in bone marrow cells (BMC ) of C3H/HeOU mice, but not in BMC from C3H/HeJ mice. We show in this study that BMC from C3H/HeJ and C57BL/10ScCr mice do not express CD14 after expo sure to LPSs from Salmonella enterica and Bordetella pertussis, but do expr ess this marker when treated with several LPSs from Rhizobiaceae, or their lipid A fragments. This shows that the constitutive LPS receptor in BMC fro m C3H/HeJ and C57BL/10ScCr mice is fully able to trigger a complete signall ing cascade. Results of cross-inhibition of the binding of radiolabelled LP S indicated that active LPSs (from R. species Sin-1 and R. galegae) and ina ctive LPSs (from S. enterica and B. pertussis) bind to the same site of the constitutive LPS receptor of C3H/HeJ cells. Furthermore, binding of R. spe cies Sin-1 LPS, and signalling induced by this LPS, were both inhibited by pre-exposure of C3H/HeJ cells to B. pertussis lipid A. This correlation bet ween binding and signalling suggests that in C3H/HeJ cells, the constitutiv e receptor, which recognizes a large panel of LPSs from different origins, appears selectively unable to be activated by some particular LPSs, such as those of Enterobacteria and Bordetella.