Differential role of interferon-gamma in the potentiating effect of muramyl peptides for enhanced responses to lipopolysaccharide in mice: effect of cyclosporin A

Expression and regulation of the pattern recognition receptors Toll-like receptor-2 and Toll-like receptor-4 in the human placenta

The placenta constitutes a physical and immunological barrier against invading infectious agents and has been suggested to be a pregnancy-specific component of the innate immune system. The aim of this study was to investigate the presence and regulation of Toll-like receptors-2 and -4 (TLR2 and TLR4) in the human placenta, because these receptors are believed to be important for immune responses against pathogens. Twenty-eight placentas from normal term pregnancies were analysed with immunohistochemistry, which showed a strong immunoreactivity for TLR2 and TLR4 in the villous and the intermediate trophoblasts. The regulation of TLR2 and TLR4 by microbial stimulus was assessed by incubating explants of term chorionic villi with zymosan or lipopolysaccharide (LPS) and analysed with real-time reverse transcriptase-polymerase chain reaction. Stimulation with zymosan and LPS readily induced interleukin (IL)-6 and IL-8 cytokine production in the placenta cultures, whereas TLR2 and TLR4 mRNA and protein expression remained at the same high level as in unstimulated explants. These data suggests a novel mechanism for the fetoplacental unit to interact with micro-organisms.

Regulation of lipopolysaccharide-induced tumor necrosis factor production by cyclosporin A in mice primed with muramyl dipeptide

The effect of cyclosporin A (CsA) on tumor necrosis factor (TNF) or interleukin-6 (IL-6) production was evaluated in vivo in primed or unprimed mice challenged with lipopolysaccharide (LPS). Both pretreatment with BCG infection or with muramyl dipeptide (MDP) prior to LPS challenge resulted in an increase in the cytokine bioactivity level in the blood. CsA administration inhibited the TNF production. In unprimed mice, either normal or sensitized to LPS lethality by galactosamine treatment, a marked decrease in the cytokine level was observed after injection of CsA. After adrenalectomy, the yield of both TNF and IL-6 following LPS injection was markedly elevated but decreased by CsA administration. Ex vivo experiments have shown that the inhibitory effect of CsA could be demonstrated at the level of macrophages from mice previously given the drug. If mice had received MDP, in vitro responses of cells to LPS were enhanced but again CsA decreased the mRNA expression and protein secretion.