Comparison of monocyte functions after LPS- or IL-10-induced reorientation: importance in clinical immunoparalysis

Immunoparalysis is an acquired immunodeficiency which may occur in patients after major surgery, burns, polytrauma and sepsis. It is associated with a modified state of monocytes marked by their altered capacity to induce antigen-specific T cell stimulation and to release various cytokines. However, the pathogenesis of immunoparalysis may differ in various patient groups. It can develop in patients after systemic hyperinflammation induced by gastrointestinal translocation of endotoxin (lipopolysaccharide, LPS) or sepsis, as well as in patients without preceding systemic inflammation but primary anti-inflammation, for instance induced by sympathetic activation. To further elucidate the syndrome, we compared endotoxin tolerance as a model of immunoparalysis after systemic hyperinflammation versus interleukin-10 (IL-10) treatment as a model of primarily anti-inflammation-induced immunoparalysis. In vitro priming of peripheral blood mononuclear cells with either LPS or IL-10 for 24 h led to a strongly or moderately diminished LPS-induced tumor necrosis factor-alpha (TNF-alpha) production, compared to unprimed controls, respectively. Furthermore, LPS-induced reduction of TNF-alpha production capacity persisted over the following days whereas IL-10-primed monocytes rapidly recovered. Similarly, in contrast to persistently diminished MHC class II expression in LPS-treated monocytes, IL-10 only transiently downregulated these molecules. Consequently, in contrast to IL-10-primed monocytes, LPS-primed monocytes were greatly impaired in their capacity to induce antigen-specific T cell proliferation and IFN-gamma production. These data indicate that LPS priming provokes a more profound modulation of monocyte function than IL-10 priming, raising the question of possible variations in the clinical course of immunoparalysis, dependent on its pathogenesis.