Augmented TNF-alpha and IL-10 production by primed human monocytes following interaction with oxidatively modified autologous erythrocytes.

The presence of dysfunctional/damaged red blood cells (RBCs) has been associated with adverse clinical effects during the inflammatory response. The aim of this study was to elucidate whether oxidatively modified, autologous RBCs modulate monocyte cytokine responses in humans. Monocyte tumor necrosis factor alpha (TNF-alpha) and IL-10 production was measured in whole blood from healthy volunteers using ELISA and flow cytometry. Oxidatively modified RBCs (15 mM phenylhydrazine, 1 h, OX-RBC) or vehicle-treated RBCs (VT-RBC) opsonized by autologous serum were administered alone or in combination with one of three priming agents: E. coli lipopolysaccharide (LPS, 0.2 ng/ml), zymosan A (1 mg/ml), or phorbol 12-myristate 13-acetate (PMA, 50 ng/ml). OX-RBC or VT-RBC alone did not result in the release of TNF-alpha or IL-10. LPS, zymosan, and PMA caused marked and dose-dependent increases in TNF-alpha and IL-10 production. Addition of OX-RBC augmented the LPS-, zymosan-, and PMA-induced TNF-alpha release by approximately 100%. OX-RBC augmented LPS- and zymosan-induced IL-10 release by 400-600%. Flow cytometry analyses showed that monocytes were responsible for TNF-alpha and IL-10 production in whole blood. The presence of OX-RBC alone increased the complexity of CD14+ monocytes but caused no cytokine production. LPS alone induced cytokine production without altering cell complexity. After the combined (OX-RBC+LPS) treatment, monocytes of high complexity were responsible for TNF-alpha production. The presence of mannose or galactose (at 10-50 mM) did not alter the observed augmentation of cytokine production by OX-RBC, suggesting that lectin receptors are not involved in the response. These studies indicate that the interaction between damaged autologous erythrocytes and monocytes has a major impact on the cytokine responses in humans. An augmented cytokine production by the mononuclear phagocyte system may adversely affect the clinical course of injury and infections especially in genetic or acquired RBC diseases or after transfusions.

Cutting edge: IFN-inducible ELR- CXC chemokines display defensin-like antimicrobial activity.

Recent reports highlighted the chemotactic activities of antimicrobial peptide defensins whose structure, charge, and size resemble chemokines. By assaying representative members of the four known families of chemokines we explored the obverse: whether some chemokines exert antimicrobial activity. In a radial diffusion assay, only recombinant monokine induced by IFN-gamma (MIG/CXCL9), IFN-gamma-inducible protein of 10 kDa (IP-10/CXCL10), and IFN-inducible T cell alpha chemoattractant (I-TAC/CXCL11), members of the IFN-gamma-inducible tripeptide motif Glu-Leu-Arg (ELR)(-) CXC chemokines, were antimicrobial against Escherichia coli and Listeria monocytogenes. Similar to human defensins, antimicrobial activities of the chemokines were inhibited by 50 and 100 mM NaCl. The concentration of MIG/CXCL9 and IP-10/CXCL10 released from IFN-gamma-stimulated PBMC in 24 h were, respectively, 35- and 28-fold higher than from unstimulated cells. Additionally, the amounts of chemokines released per monocyte suggest that, in tissues with mononuclear cell infiltration, IFN-gamma-inducible chemokines may reach concentrations necessary for microbicidal activity. IFN-gamma-inducible chemokines may directly inactivate microbes before attracting other host defense cells to the area of infection.