Cellular immune suppression in cancer patients and its implication for dendritic cell therapy

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Background: The treatment of human cancer with monocyte-derived dendritic cells (MoDC) is a promising and innovative approach. However, many of the treated patients fail to respond to therapy. The reduced clinical antitumor response may be due to an inflammatory immune-suppressive tumor microenvironment. Regulatory T-cells (T-reg) and other cells with suppressive potential can promote an immune suppressive tumor microenvironment and thus play an important role in regulation of the immune response. Methods: Whole blood from n=100 cancer patients with various tumor types and from n=30 healthy donors were analysed by flow cytometry. CD4+ lymphocytes with immune suppressive potential were characterized by analysing the expression of CD25, CD39, CD127. Results: We found a significantly higher proportion of CD25+/CD39+ and of CD25+/CD127low T-helper cells in the blood of cancer patients as compared to healthy donors. This may indicate two different types of T-reg involved in immune suppression in cancer patients. Treatment of patients with metronomic chemotherapy induced a down-regulation of these cells. Interestingly, we found a subpopulation of cells within the lymphocyte gate characterized by CD2high and CD86 expression in cancer patients with very advanced stage, similar to such normally found in hemaphagocytic lymphohistiocytosis (HLH) patients characterized by exceeding high plasma concentration of IFN-g and IL-10 (Schneider et al. 2002). These cells can be down-regulated by treatment with a tetradecapeptide (Ezrin) known to act as an immune modulator with anti-viral activity leading to reduction of inflammatory cytokines. Conclusions: An efficient induction of a clinical antitumor response requires both a polarization of MoDC in a TH1 direction as well as changing an immune suppressive tumor microenvironment. For the first time, we identified HLH associated cells in advanced cancer patients. As HLH is characterized by hyperinflammation, these cells may indicate an inflammatory tumor microenvironment. Thus, anti-inflammatory therapy should be considered as co-treatment with immunotherapy with dendritic cells for down-regulation of immune suppressive cells (T-reg, CD2high/CD86+ cells) to promote a clinical antitumor response.

No significant financial relationships to disclose.

Neisseria gonorrhoeae porin modifies the oxidative burst of human professional phagocytes

A hallmark of infection with the gram-negative bacterium Neisseria gonorrhoeae is the local infiltration and subsequent activation of polymorphonuclear neutrophils. Several gonococcal outer membrane proteins are involved in the interaction with and the activation of these phagocytes, including gonococcal porin, the most abundant protein in the outer membrane. Previous work suggests that this porin plays a role in various cellular processes, including inhibiting neutrophils activation and phagosome maturation in professional phagocytes. Here we investigated the ability of porin to modify the oxidative metabolism of human peripheral blood neutrophils and monocytes in response to particulate stimuli (including live gonococci) and soluble agents. The activation of the oxidative metabolism was determined by chemiluminescence amplified with either luminol or lucigenin. We found that treatment of the phagocytes with porin inhibits the release of reactive oxygen species measured as luminol-enhanced chemiluminescence in response to zymosan, latex particles, and gonococci. The engulfment of these particles was not, however, affected by porin treatment. Similar effects of porin on the chemiluminescence response were observed in cytochalasin B-treated neutrophils exposed to the soluble chemotactic peptide N-formylmethionyl-leucyl-phenylalanine. This indicates that porin selectively inhibits granule fusion with those cellular membranes that are in direct contact with porin, namely, the phagosomal and plasma membranes. This porin-induced downregulation of oxidative metabolism may be a potent mechanism by which gonococci modulate oxygen-dependent reactions by activated phagocytes at inflammation sites.

Differential Opa specificities for CD66 receptors influence tissue interactions and cellular response to Neisseria gonorrhoeae

The ability of all 11 variable opacity (Opa) proteins encoded by Neisseria gonorrhoeae MS11 to interact directly with the five CD66 antigens was determined. Transfected HeLa cell lines expressing individual CD66 antigens were infected with recombinant N. gonorrhoeae and Escherichia coli strains expressing defined Opas. Based upon the ability of these bacteria to bind and invade and to isolate specifically CD66 antigens from detergent-soluble extracts of the corresponding cell lines, distinct specificity groups of Opa interaction with CD66 were seen. Defining these specificity groups allowed us to assign a specific function for CD66a in the Opa-mediated interaction of gonococci with two different target cell types, which are both known to co-express multiple CD66 antigens. The competence of individual Opas to interact with CD66a was strictly correlated with their ability to induce an oxidative response by polymorphonuclear neutrophils. The same Opa specificity was observed for the level of gonococcal binding to primary endothelial cells after stimulation with TNFalpha, which was shown to increase the expression of CD66a rather than CD66e. As CD66e alone is expressed on other target tissues of gonococcal pathogenicity, Opa variation probably contributes to the cell tropism displayed by gonococci.