A comparison of the effects of intact and deacylated lipopolysaccharide on human polymorphonuclear leukocytes

Enzymatic deacylation of LPS markedly reduces its activity in the dermal Schwartzman reaction. Inasmuch as polymorphonuclear leukocytes (PMN) are involved in the genesis of tissue injury in Shwartzman reactions, we have investigated the effects of deacylated LPS (dLPS) on PMN. Compared to LPS, dLPS was ineffectual as a stimulus of both PMN adherence and release of secondary granule enzymes, and dLPS inhibited specific LPS-induced adherence. Neither LPS nor dLPS caused release of the primary granule enzymes, myeloperoxidase, and elastase. Unlike LPS, dLPS failed to prime PMN for superoxide release when a second stimulus (FMLP, 10^-6 M) was given. The mechanism of the LPS induced increase in PMN adherence was investigated, and we found that LPS significantly increased the amount of the adhesive glycoprotein CD11b on the surface of the PMN. dLPS had no effect on CD11b expression. Our results suggest that enzymatic deacylation of LPS profoundly alters its ability to stimulate PMN and deacylation of LPS by inflammatory cells in vivo might be an important mechanism limiting the toxic effects of LPS.