Enhancement of macrophage candidacidal activity by interferon-gamma. Increased phagocytosis, killing, and calcium signal mediated by a decreased number of mannose receptors

Involvement of mannose receptor in cytokine interleukin-1beta (IL-1beta), IL-6, and granulocyte-macrophage colony-stimulating factor responses, but not in chemokine macrophage inflammatory protein 1beta (MIP-1beta), MIP-2, and KC responses, caused by attachment of Candida albicans to macrophages

The production of chemotactic cytokines (chemokines) and other cytokines by macrophages in response to fungal infection is thought to be critical during the course of candidiasis. However, the mechanism of cytokine synthesis by macrophages in response to fungi is not well understood. Therefore, the response of macrophages to Candida albicans was examined in terms of receptor-mediated chemokine and other cytokine mRNA induction. Attachment of C. albicans to murine thioglycollate-elicited peritoneal macrophages induced increased mRNA levels of the cytokines interleukin-1beta (IL-1beta), IL-6, and granulocyte-macrophage colony-stimulating factor (GM-CSF) and the chemokines macrophage inflammatory protein 1beta (MIP-1beta), MIP-2, and KC (a member of the platelet factor 4 neutrophil chemoattractant family), as determined by quantitative reverse transcription-PCR. However, treatment of macrophages with alpha-methyl-D-mannoside significantly reduced the cytokine GM-CSF response to C. albicans but did not affect the chemokine MIP-2 response. Antisense oligodeoxynucleotide (ODN) to mannose receptor (MR) mRNA inhibited the expression and function of MR in macrophages as determined by Western blot analysis and 125I-labeled mannose-bovine serum albumin (BSA) binding, and also inhibited the elevation of cytokine IL-1beta, IL-6, and GM-CSF mRNA levels induced by C. albicans attachment. Elevation of chemokine MIP-1beta, MIP-2, and KC mRNA levels induced by C. albicans was not affected in macrophages whose MR expression was suppressed by antisense ODN treatment. Furthermore, IL-4 treatment of macrophages, which up-regulated MR expression as determined by Western blot analysis and fluorescein isothiocyanate-labeled mannose-BSA uptake, enhanced the level of cytokine GM-CSF mRNA induced by C. albicans but not the level of the chemokine MIP-2 mRNA. These results indicate that selected cytokine responses of macrophages to C. albicans are mediated by MR, while some chemokine responses may be mediated by other receptors.

gamma Interferon gene expression and release in human lymphocytes directly activated by Cryptococcus neoformans and Candida albicans

Previous studies in our laboratory and others have demonstrated that T and/or NK cells can directly bind to and inhibit the growth of the medically important fungal pathogens Cryptococcus neoformans and Candida albicans by apparently non-major histocompatibility complex-restricted mechanisms. Here, we examined whether this direct interaction between lymphocytes and fungi also results in cytokine gene expression and release. Nonadherent lymphocytes (NAL), isolated from human peripheral blood mononuclear cells by depletion of cells adherent to plastic and nylon wool, released gamma interferon (IFN-gamma), but not interleukin-4 (IL-4) and IL-10, following stimulation with C. neoformans yeast cells and C. albicans yeast cells, hyphae, and supernatants. The fungal stimuli also induced IFN-gamma mRNA, with peak gene expression seen at or after 18 h. IFN-gamma release was still seen even when either NK cells or T lymphocytes were depleted by negative selection, suggesting that both cell types can be stimulated by fungi to produce IFN-gamma. Release of IFN-gamma from fungus-stimulated NAL occurred in the absence of an intact complement system and was not especially enhanced by culture with IL-2 or IL-12. These data expand the mechanisms by which the direct interaction of NAL with fungal targets can lead to immune activation. Moreover, to our knowledge, this is the first demonstration of direct stimulation of T-cell cytokine release by microbial pathogens.

Effects of interleukin-10 on human peripheral blood mononuclear cell responses to Cryptococcus neoformans, Candida albicans, and lipopolysaccharide

Deactivation of mononuclear phagocytes is critical to limit the inflammatory response but can be detrimental in the face of progressive infection. We compared the effects of the deactivating cytokine interleukin 10 (IL-10) on human peripheral blood mononuclear cell (PBMC) responses to lipopolysaccharide (LPS), Cryptococcus neoformans, and Candida albicans. IL-10 effected dose-dependent inhibition of tumor necrosis factor alpha (TNF-alpha) release in PBMC stimulated by LPS and C. neoformans, with significant inhibition seen with 0.1 U/ml and greater than 90% inhibition noted with 10 U/ml. In contrast, even at doses as high as 100 U/ml, IL-10 inhibited TNF-alpha release in response to C. albicans by only 50%. IL-10 profoundly inhibited release of IL-1beta from PBMC stimulated by all three stimuli. TNF-alpha mRNA and release was inhibited even if IL-10 was added up to 8 h after cryptococcal stimulation. In contrast, inhibition of IL-1 beta mRNA was of lesser magnitude and occurred only when IL-10 was added within 2 h of cryptococcal stimulation. IL-10 inhibited translocation of NF-kappaB in response to LPS but not the fungal stimuli. All three stimuli induced IL-10 production in PBMC, although over 10-fold less IL-10 was released in response to C. neoformans compared with LPS and C. albicans. Thus, while IL-10 has deactivating effects on PBMC responses to all three stimuli, disparate stimulus- and response-specific patterns of deactivation are seen. Inhibition by IL-10 of proinflammatory cytokine release appears to occur at the level of gene transcription for TNF-alpha and both transcriptionally and posttranscriptionally for IL-1beta.

Production and function of cytokines in natural and acquired immunity to Candida albicans infection

Host resistance against infections caused by the yeast Candida albicans is mediated predominantly by polymorphonuclear leukocytes and macrophages. Antigens of Candida stimulate lymphocyte proliferation and cytokine synthesis, and in both humans and mice, these cytokines enhance the candidacidal functions of the phagocytic cells. In systemic candidiasis in mice, cytokine production has been found to be a function of the CD4+ T helper (Th) cells. The Th1 subset of these cells, characterized by the production of gamma interferon and interleukin-2, is associated with macrophage activation and enhanced resistance against reinfection, whereas the Th2 subset, which produces interleukins-4, -6, and -10, is linked to the development of chronic disease. However, other models have generated divergent data. Mucosal infection generally elicits Th1-type cytokine responses and protection from systemic challenge, and identification of cytokine mRNA present in infected tissues of mice that develop mild or severe lesions does not show pure Th1- or Th2-type responses. Furthermore, antigens of C. albicans, mannan in particular, can induce suppressor cells that modulate both specific and nonspecific cellular and humoral immune responses, and there is an emerging body of evidence that molecular mimicry may affect the efficiency of anti-Candida responses within defined genetic contexts.

Enhancement of phagocytosis by dynorphin A in mouse peritoneal macrophages

The effects of the opioid peptide dynorphin A (DynA) on phagocytosis in peritoneal macrophages was examined by flow cytometry (FCM). DynA enhanced phagocytosis in a dose-dependent manner. Leucine-enkephalin (Leu-Enk), methionine-enkephalin (Met-Enk), beta-neo-endorphin (beta Neo-End), DynA(9-17) and DynA(13-17) had no such activity. Alpha-Neo-endorphin (alpha Neo-End), dynorphin B (DynB), DynA(1-13) and DynA(6-17) enhanced phagocytosis less effectively than DynA. Naloxone did not inhibit the enhancement of phagocytosis induced by DynA. Unstimulated control phagocytosis was partially suppressed in Ca2+-free EGTA-containing solution and even in this solution DynA enhanced phagocytosis. However, the enhancement by DynA was suppressed in EGTA- and BAPTA-AM-containing Ca2+-free solution. The present study showed that enhancement of phagocytosis by DynA was independent of extracellular Ca2+ ([Ca2+]o) and dependent on intracellular Ca2+ ([Ca2+]i). The present results support DynA being one of the mediators from the nervous system that modulates the immune system.

Gamma delta T cell-induced nitric oxide production enhances resistance to mucosal candidiasis

Despite the prevalence of gamma delta T cells in mucosae that are typically colonized by Candida albicans, little is known of the possible role of these cells in resistance to candidiasis. A sharp increase in the number of gamma delta T cells and macrophages following intraperitoneal inoculation of mice with C. albicans led us to examine the role of these cells in the immune response to C. albicans. We show that the gamma delta T cells enhance macrophage nitric oxide (NO) production and anti-candida activity, in vitro. We also propose that the gamma delta T cells regulate macrophage function during candidiasis in vivo as well, because depletion of these cells abrogated inducible NO synthase expression in mucosae and enhanced murine susceptibility to candidiasis.

Impaired response of activated mononuclear phagocytes to interleukin 4 in inflammatory bowel disease

BACKGROUND/AIMS

In inflammatory bowel disease (IBD), peripheral monocytes and intestinal macrophages show an increased state of priming and activation. The aim of this study was to test the hypothesis that the response of IBD mononuclear phagocytes to the contrainflammatory cytokine interleukin (IL) 4 may be altered.

METHODS

The in vitro secretion of proinflammatory cytokines (IL-1 beta, tumor necrosis factor alpha [TNF-alpha], and IL-1-receptor antagonist [IL-1ra]) by peripheral monocytes and by intestinal lamina propria mononuclear cells (LPMNCs) was assessed by enzyme-linked immunosorbent assay. In parallel, superoxide anion release, macrophage mannose receptor, and IL-4 receptor expression were investigated.

RESULTS

IBD peripheral monocytes and intestinal LPMNCs in vitro secrete increased amounts of proinflammatory cytokines (IL-1 beta and TNF-alpha) with decreased IL-1ra/IL-1 beta ratios. IL-4 down-regulates proinflammatory cytokine (IL-1 beta and TNF-alpha) and superoxide anion secretion in a dose-dependent manner. In contrast to normal and disease-specific controls, IBD peripheral monocytes and IBD intestinal LPMNCs show a diminished responsiveness to the inhibitory effect of IL-4. The IL-1ra/IL-1 beta ratios in normal monocytes are increased by IL-4, whereas in IBD monocytes low IL-1ra/IL-1 beta ratios persist after IL-4 treatment. IL-4-induced expression of macrophage mannose receptor, which is a molecule pivotal to macrophage-mediated host defense, again appeared to be impaired in IBD monocytes.

CONCLUSIONS

IL-4-mediated regulation of mononuclear phagocyte effector functions is disturbed in IBD.

Effects of naftifine and terbinafine, two allylamine antifungal drugs, on selected functions of human polymorphonuclear leukocytes

Many antimycotic agents negatively affect the natural immune response. Typically, these drugs impair polymorphonuclear leukocyte (PMN) production of superoxide anion, chemotaxis, or the killing of pathogens. Allylamines are a new class of antimycotic compounds with a new mechanism of antifungal action, i.e., inhibition of the fungal squalene epoxidase. The trial that we describe aimed to evaluate the effects of two allylamines, terbinafine and naftifine, on selected functions of PMNs, i.e., superoxide anion production, chemotaxis, and killing of Candida albicans blastospores. Terbinafine and naftifine on their own did not affect superoxide anion production when they were added to PMNs. When PMNs were preincubated with allylamines and were then stimulated by N-formyl-Met-Leu-Phe or phorbol 12-myristate 13-acetate, superoxide anion production was increased (priming effect). Since intracellular free calcium (Ca2+i) is involved in the control of superoxide anion production, we evaluated the effects of the allylamines on the Ca2+i concentration ([Ca2+]i). In the presence of terbinafine or naftifine, the [Ca2+]i increased in a dose-dependent manner; the source of Ca2+i was not extracellular since it was not affected by extracellular calcium chelation with ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid. In the presence of terbinafine or naftifine, chemotaxis of PMNs was not impaired. Terbinafine and naftifine slightly but significantly increased the killing of C. albicans blastospores (P < 0.05 at 10 and 100 microM). In conclusion, in contrast to imidazole-like drugs, the allylamine antimycotic compounds terbinafine and naftifine enhance selected functions of PMNs.