In vitro and in vivo immune stimulating effects of a new standardized Echinacea angustifolia root extract (Polinacea).

Polinacea is a new standardized hydroethanolic extract obtained from Echinacea angustifolia roots containing echinacoside (>4%), the high molecular weight polysaccharide IDN 5405 (>5%) and a isobutylamide fraction (<0.1%). For in vitro tests, a bacterial lipopolysaccharide-free (LPS-free) Polinacea has been prepared in order to avoid non-specific responses of immunocompetent cells. LPS-free Polinacea enhanced the immune functions as highlighted by the proliferation rate and gamma-interferon production in murine T-lymphocyte cell cultures stimulated by anti-CD3. LPS-free Polinacea did not have a direct role on macrophage response as measured in the nitric oxide production test using the J774 macrophage cells line. In vivo, Polinacea showed an immune stimulating activity by reducing the Candida albicans induced mortality both in normal and in cyclosporin A-treated mice.

IL-10 enhances CCL2 release and chemotaxis induced by CCL16 in human monocytes.

CCL16 is a CC chemokine originally identified as a liver-expressed chemokine. Its expression has been detected in activated monocytes where it is up-regulated by stimulation with IL-10. This is in contrast with IL-10's inhibition of the expression of most chemokines. CCL16 is chemotactic for monocytes, lymphocyte and dendritic cells. We investigated whether CCL16 displays biological activities other than chemotaxis and whether IL-10 affects monocyte response to CCL16. We show that CCL16 induces the expression of CCL2 at the mRNA and protein level, but does not affect that of CCL5, CCL18 and proinflammatory cytokines. This effect was prevented by treatment with pertussis toxin and may thus be mediated by G-protein-coupled receptors. IL-10 markedly increased CCL2 production induced by CCL16, but suppressed that of CXCL8. It also enhanced the chemotactic response to CCL16. Addition of antibodies blocking CCR1, but not CCR8, prevented this enhanced chemotactic response and suggested that CCR1 is primarily involved. We propose that IL-10 modulates the effects of CCL16 on monocytes by increasing their CCR1-dependent response. The coordinated secretion of CCL16 and IL-10 may thus enhance monocyte infiltration.

Interaction of Bartonella henselae with the murine macrophage cell line J774: infection and proinflammatory response.

Bartonella henselae is the causative agent of cat scratch disease (CSD), a self-limiting condition characterized by a subacute regional lymphadenopathy that may develop into disseminated bartonellosis in immunocompromised subjects. Mice experimentally infected with B. henselae display typical liver and spleen granulomas rich in T cells and macrophages. So far there are no data on the interaction between bartonellae and macrophages. In order to clarify this topic, we investigated the interaction of B. henselae with J774, a mouse macrophage cell line. Analysis of bacterial uptake by functional assays and transmission electron microscopy indicates that bartonellae can enter and survive inside J774. Entry occurred within 30 min postinfection and reached a plateau at 160 min. Infection of J774 was followed by a dose-dependent release of the proinflammatory cytokines tumor necrosis factor alpha, interleukin 1beta (IL-1beta), and IL-6. Bartonellae persisted intracellularly without loss of viability for at least 8 h, and their number slightly decreased 24 h postinfection. Gamma interferon (IFN-gamma) treatment of J774 significantly decreased the number of recoverable bacteria at 8 and 24 h. This enhancement of macrophage bactericidal activity was associated with nitric oxide (NO) release and was prevented by the addition of the competitive inhibitor of NO synthesis N(G)-monomethyl L-arginine. These findings suggest that IFN-gamma-mediated activation of macrophages may be important for the clearing of B. henselae infection and that anti-B. henselae microbicidal activity of IFN-gamma-activated macrophages is mediated to a large extent by NO production.

Serum amyloid A is an activator of PMN antimicrobial functions: induction of degranulation, phagocytosis, and enhancement of anti-Candida activity.

Serum amyloid A (SAA) is a 12-kDa protein secreted in large amounts by liver cells during microbial infections or inflammatory diseases. We have recently reported that SAA induces chemotaxis of polymorphonuclear cells (PMN), monocytes, and T lymphocytes and stimulates their adhesion to endothelial monolayers. In this study, we investigated whether SAA regulates PMN antimicrobial activities. We found that recombinant SAA (rSAA), at concentrations comparable to serum levels attained during an acute phase response, is a potent activator of PMN. Stimulation of PMN by rSAA results in a rapid and transient increase of cytosolic calcium concentration and up-regulation of cell-surface expression of antigens involved in adhesion and microbial recognition such as CD11c and CD16. In addition, stimulation of PMN with rSAA increases secretion of lactoferrin, an antimicrobial protein that is contained in specific granules of PMN and enhances PMN phagocytic activity against heat-killed Candida albicans. Finally, activation of PMN with rSAA enhances their anti-Candida activity within 30 min of stimulation. These results suggest that SAA is involved in up-regulating PMN antimicrobial activities and that high circulating concentrations of SAA as seen in the acute phase response may constitute a potential host defense mechanism against fungal infections.