Differential effects of granulocyte/macrophage colony-stimulating factor (GM-CSF) in enhancing macrophage resistance to Legionella pneumophila vs Candida albicans

The effects of fluconazole and cytokines on human mononuclear cells

Candida infections are common infections and fluconazole is one of the most frequently administered antifungal agents in their treatment. The resistance developed against antifungal agents has necessitated the improvement of new treatments. This study focuses on the investigation of the effect of fluconazole and cytokines such as interferon-gamma (IFN-gamma), tumor necrosis factor-alpha (TNF-alpha), granulocyte-macrophage colony-stimulating factor (GM-CSF) on chemokine production and anticandidal activity of human monocytes. In the study it was observed that GM-CSF caused an increase in candidacidal activity of monocytes. Anticandidal activity of GM-CSF + IFN-gamma combination was not found to be more effective than GM-CSF or IFN-gamma alone. The presence of cytokine and fluconazole caused an increase in the levels of CCL3 and CCL4 chemokines. Accordingly, it was considered that chemokines could contribute to the efficacy of fluconazole in C. albicans infections. Besides, in order to strengthen the immune system some cytokines might be used in addition to antifungal agents for the treatment.

Effects of cytokines and fluconazole on the activity of human monocytes against Candida albicans

This study evaluates the effects of cytokines, used singly and in combination, on the microbicidal activity of human monocyte-derived macrophages (MDM) against intracellular Candida albicans in the presence and absence of fluconazole. In the absence of fluconazole, the addition of tumor necrosis factor alpha (TNF-alpha), interleukin-1beta (IL-1beta), gamma interferon (IFN-gamma), or IL-4 had no effect on the growth of C. albicans. In contrast, the addition of granulocyte-macrophage colony-stimulating factor (GM-CSF) resulted in decreased growth (P < 0.05), while the addition of IL-10 resulted in increased growth (P < 0.01). In the presence of fluconazole, only the addition of IFN-gamma resulted in an increase in the growth of C. albicans. In the presence or absence of fluconazole, all cytokine combinations except IFN-gamma plus GM-CSF caused significant decreases in growth (P < 0.01). IL-10 and IL-4 did not influence the activity of TNF-alpha or IL-1beta. In the absence or presence of C. albicans the addition of fluconazole, all of the cytokines studied, and combinations of fluconazole and selected cytokines caused increases in nitric oxide (NO) production (P < 0.01). Similar observations were made for superoxide (O(2)(-)) only in the presence of C. albicans. The greatest concentrations of NO and O(2)(-) were produced when C. albicans alone was present in the assays. Our results demonstrate that in the presence of low concentrations of fluconazole (0.1 times the MIC), selected cytokines and their combinations significantly increase the microbicidal activity of MDM against intracellular C. albicans.

Glycyrrhizin improves the resistance of MAIDS mice to opportunistic infection of Candida albicans through the modulation of MAIDS-associated type 2 T cell responses

Compared with normal mice, MAIDS mice (mice infected with LP-BM5 murine leukemia virus) exhibited an increase up to 100 times greater in susceptibility to infection with Candida albicans. The impaired resistance of MAIDS mice to the infection was recovered to levels observed in normal mice by the administration of glycyrrhizin (GR), an active component of licorice roots. MAIDS mice inoculated with CD4(+) T cells from GR-treated mice were also resistant to C. albicans infection. Normal mice inoculated with CD4(+) T helper type 2 cells (Th2 cells) from MAIDS mice were susceptible to C. albicans infection at the same levels shown in MAIDS mice. The susceptibility of normal mice inoculated with type 2 T cells was reversible by (i) administration of GR and (ii) inoculation of CD4(+) T cells from GR-treated mice and injection of a mixture of mAbs targeted against type 2 cytokines (IL-4 and IL-10). Type 2 cytokines were not detected in sera of MAIDS mice inoculated with CD4(+) T cells from GR-treated mice, while they were present in sera of MAIDS mice treated with saline. These results suggest that, by inducing CD4(+) T cells which suppress type 2 cytokine production by MAIDS-associated Th2 cells, GR improves the resistance of MAIDS mice to C. albicans infection.

Obligatory role of gamma interferon for host survival in a murine model of infection with Burkholderia pseudomallei

Burkholderia pseudomallei, the causative agent of melioidosis, is a gram-negative bacterium capable of causing either acute lethal sepsis or chronic but eventually fatal disease in infected individuals. However, despite the clinical importance of this infection in areas where it is endemic, there is essentially no information on the mechanisms of protective immunity to the bacterium. We describe here a murine model of either acute or chronic infection with B. pseudomallei in Taylor Outbred (TO) mice which mimics many features of the human pathology. Intraperitoneal infection of TO mice at doses of >10(6) CFU resulted in acute septic shock and death within 2 days. In contrast, at lower doses mice were able to clear the inoculum from the liver and spleen over a 3- to 4-week period, but persistence of the organism at other sites resulted in a chronic infection of between 2 and 16 months duration which was eventually lethal in all of the animals tested. Resistance to acute infection with B. pseudomallei was absolutely dependent upon the production of gamma interferon (IFN-gamma) in vivo. Administration of neutralizing monoclonal antibody against IFN-gamma lowered the 50% lethal dose from >5 x 10(5) to ca. 2 CFU and was associated with 8,500- and 4,400-fold increases in the bacterial burdens in the liver and spleen, respectively, together with extensive destruction of lymphoid architecture in the latter organ within 48 h. Neutralization of either tumor necrosis factor alpha or interleukin-12 but not granulocyte-macrophage colony-stimulating factor, also increased susceptibility to infection in vivo. Together, these results provide the first evidence of a host protective mechanism against B. pseudomallei. The rapid production of IFN-gamma within the first day of infection determines whether the infection proceeds to an acute lethal outcome or becomes chronic.

The potential for monocyte-mediated immunotherapy during infection and malignancy--Part II: in vivo activation by exogenous cytokines and clinical applications

The monocyte system exhibits a range of immunological mechanisms that may be harnessed for therapeutic effect against infection and malignancy. The advent of novel therapies aimed at treating infection and malignancy is complemented by a resurgence of clinical interest in immunotherapeutic programmes to treat diseases by modification or direct augmentation of host immunity. Cytokines such as granulocyte-macrophage colony-stimulating factor (GM-CSF) and IFN-gamma modulate the function of monocytes and have been used to experimentally probe the immunotherapeutic potential of monocytes against micro-organisms and malignancy. However, monocytes rarely act alone but communicate with other leukocytes involved in cell-mediated immunity. In particular monocytes cooperate with the T-helper (Th1 and Th2) sub-populations of peripheral lymphocytes. Moreover, sub-populations of monocytes, as identified by the co-expression of membrane-associated CD14 and CD16, have been shown to exist. At the preclinical level, this provides a unique opportunity to explore the effect of immunotherapeutic strategies on the function of monocyte sub-populations against infectious or malignant challenge and may allow immunotherapeutic strategies to be targeted towards specific monocyte sub-populations. Preclinical and clinical studies in human subjects suggest that GM-CSF and other cytokines such as IFN-gamma are the most promising biological response modifiers for augmenting monocyte-mediated immunity. In this review, the immunotherapeutic potential of the monocyte system will be discussed in the context of combating microbial and malignant disease.

Thermal injury induces the development of inflammatory macrophages from nonadherent bone marrow cells

The normal course of hematopoiesis is controlled by growth factors and cytokines and, therefore, should be susceptible to alterations induced by systemic mediator release such as that seen following thermal injury. We hypothesized that a brief exposure of developing macrophages to the postthermal injury state would result in functionally altered progeny. We measured the production of inflammatory mediators by rat, bone-marrow macrophage precursors harvested 24 h following a 30% TBSA burn after subsequent maturation in a controlled, in vitro environment. Interleukin (IL)-6, tumor necrosis factor (TNF), and prostaglandin (PG) E2 levels in response to 24 h stimulation with lipopolysaccharide (LPS) were measured following 4 or 8 days of incubation with IL-3, granulocyte-macrophage colony-stimulating factor (GM-CSF), or both. Flow cytometric analysis showed that bone marrow cells harvested from burn and sham animals cultured in GM-CSF developed principally into macrophages (His48+, R21A6A+, CD11b+. Unstimulated cells produced negligent levels of cytokines and PGE2. Stimulated burn-derived cells released greater amounts of IL-6 and TNF at 4 or 8 days of culture depending on the conditions. Elevated PGE2 release was noted in all GM-CSF containing cultures, with burn-derived cells showing a trend towards reduced prostaglandin release. Detection of mRNA for cytokines after LPS stimulation showed no change in IL-6 or TNF transcripts. A short exposure to the systemic effects of thermal injury preprogramed macrophage progenitor cells with the propensity to develop into inflammatory macrophages, secreting higher levels of TNF and IL-6. This shift towards proinflammatory functions in these cells suggests they could be a source of enhanced inflammatory mediator release at 4 or more days post thermal injury.