Effect of lectins on hepatic clearance and killing of Candida albicans by the isolated perfused mouse liver.

The isolated perfused mouse liver model was used to study the effects of various lectins on hepatic trapping and killing of Candida albicans. After mouse livers were washed with 20 to 30 ml of perfusion buffer, 10(6) C. albicans CFU were infused into the livers. At the time of recovery, 63% +/- 2% (mean +/- standard error of the mean) of the infused C. albicans CFU were recovered from the liver and 14% +/- 1% were recovered from the effluent for a total recovery of 77% +/- 2%. This indicated that 86% +/- 9% of the original inoculum was trapped by the liver and that 23% +/- 2% was killed within the liver. When included in both preperfusion and postperfusion buffers (0.2 mg of lectin per ml), Ulex europeaus lectin (binding specificity for fucose) decreased hepatic trapping of C. albicans by 37% and eluted trapped C. albicans from the liver only when included in postperfusion buffer. By comparison, treatment of C. albicans with U. europeaus lectin before infusion had no effect on the trapping or killing of yeast cells. When Lens culinaris lectin (binding specificity for mannose) was included in the perfusion buffers, hepatic killing of C. albicans increased by 16% with no significant effect on hepatic killing when yeast cells were treated with L. culinaris lectin before infusion. Forty to 55% of the infused C. albicans were killed when concanavalin A (binding specificities for mannose and glucose), Glycine max (binding specificity for N-acetylgalactosamine), or Arachis hypogea (binding specificity for galactose) lectin was included in the perfusion buffer or when yeast cells were treated with these lectins before their infusion. When C. albicans was treated with concanavalin A at a concentration of less than 0.02 mg/ml, hepatic killing of yeast cells was not significantly increased. The data suggest that a fucose-containing receptor on the surface of either sinusoidal endothelial cells or Kupffer cells is involved in the trapping of C. albicans by the perfused mouse liver. Moreover, lectins with binding specificities for mannose, N-acetylgalactosamine, and galactose increased hepatic killing of C. albicans.     

Altered hepatic clearance and killing of Candida albicans in the isolated perfused mouse liver model.

The adherence of Candida albicans was studied in situ by using the perfused mouse liver model. After exhaustive washing, 10(6) C. albicans were infused into mouse livers. At the time of recovery, 62 +/- 5% (mean +/- standard error of the mean) of the infused C. albicans were recovered from the liver and 14 +/- 3% were recovered from the effluent for a total recovery of 76 +/- 4%. This indicates that 86 +/- 3% of the original inoculum was trapped by the liver and that 24 +/- 4% was killed within the liver. Chemical pretreatment of C. albicans with 8 M urea, 12 mM dithiothreitol, 2% beta-mercaptoethanol, 1% sodium dodecyl sulfate, 10% Triton X-100, or 3 M potassium chloride or enzyme pretreatment with alpha-mannosidase, alpha-chymotrypsin, subtilisin, beta-N-acetyl-glucosaminidase, pronase, trypsin, papain, or lipase did not alter adherence of C. albicans to hepatic tissue. By contrast, pepsin pretreatment significantly decreased hepatic trapping. Simultaneous perfusion with either 100 mg of C. albicans glycoprotein per liter or 100 mg of C. albicans mannan per liter also decreased trapping. Furthermore, both substances eluted previously trapped C. albicans from hepatic tissue. Chemical pretreatment with 8 M urea, 12 mM dithiothreitol, or 3 M KCI or enzymatic pretreatment with alpha-mannosidase, subtilisin, alpha-chymotrypsin, or papain increased killing of C. albicans three- to fivefold within hepatic tissue. The data suggest that mannose-containing structures on the surface of C. albicans, for example. mannans or glucomannoproteins, mediate adherence of C. albicans within the liver. Indirectly, chemical and enzymatic pretreatment renders C. albicans more susceptible to hepatic killing.     

Hepatic clearance of Candida albicans in rats.

The initial clearance of Candida albicans from the blood stream of rats and from perfusion medium by perfused rat livers was characterized. Normal rats cleared over 90% of large doses of intravenously injected yeast cells in 5 min. All were recovered as viable cells among various reticulendothelial organs after 30 min. The perfused rat liver trapped an average of 85% of the yeast cells in a single pass. No significant killing occurred, even in the presence of 10% whole rat blood. Scanning electron microscopy of cryofractured livers revealed that the cells were trapped in liver sinusoids but outside phagocytic cells.     

Role of Kupffer Cells,Complement, and Specific Antibody in Bactericidal Activities of Perfused Livers

The relative roles of Kupffer cells, complement, and specific antibody in liver antimicrobial activities were investigated by using a rat liver perfusion model. Normal livers trapped an average of 60% of Salmonella typhimurium in a single pass and in the presence of plasma killed more than 60% of these organisms in 30 min. Livers depleted of Kupffer cell function by silica treatment had significantly less bactericidal ability (ca. 15%) in the presence of plasma, showing that viable Kupffer cells are required for optimal antimicrobial activity. To determine the importance of complement in Salmonella killing, plasma complement activity was inhibited by heating at 57 and 50°C, zymosan absorption, chelation with disodium ethylenediaminetetraacetate (EDTA) and depletion of rat C3 by using specific immunoabsorbent. All treatments significantly reduced bactericidal activity in the perfused liver. Chelation of plasma with EDTA had no effect, suggesting that the alternate and not the classical pathway for complement activation was involved. Immune plasma alone was bactericidal. When immune plasma was heated, zymosan absorbed, or chelated with EDTA, bactericidal activity was inhibited in the perfused liver, but bacterial trapping increased. These results suggest that complement is required for bactericidal activity in perfused livers and that specific antibody only enhances bacterial trapping.     

Arg-Gly-Asp (RGD) peptide ameliorates carbon tetrachloride-induced liver fibrosis via inhibition of collagen production and acceleration of collagenase activity

Liver cirrhosis is caused by a relative imbalance between synthesis and degradation of collagens. Arg-Gly-Asp (RGD) peptide is a major adhesive domain of several extracellular matrix (ECM) components, such as that involved in the binding of fibronectin to the alpha5beta1 integrin receptor. We previously reported that RGD peptide increased the expression of matrix metalloproteinase in hepatic stellate cells (HSCs) which play a major role in hepatic fibrosis. We evaluated whether RGD-peptides inhibit the progression of liver fibrosis in an animal model of carbon tetrachloride-induced hepatotoxicity. RGD peptide (GRGDS) (1 mg/kg body weight) was injected intraperitoneally (i.p.) 3 times a week for one month. The group treated with control peptide (GRGES) showed pathologically typical hepatic fibrosis, while the RGD-treated group showed minimal fibrotic changes. The liver contents of collagen and hydroxyproline in the RGD-treated group was significantly lower than that of the control group. Collagenase activity measured in liver homogenates was significantly higher in the treated group than in the control group. In an in vitro study using TWNT-4 cells derived from human HSCs, RGD peptide (100 mug/ml) reduced the expression of type I collagen and tissue inhibitor of matrix metalloproteinase-1, and increased that of matrix metalloproteinase-1. These results indicated that RGD peptides inhibited liver fibrosis associated with both decreased collagen production and increased collagenase acitivity, and suggested that RGD peptide might be useful for the therapy of hepatic fibrosis.     

In situ separation of bacterial trapping and killing functions of the perfused liver.

CF-1 mice cleared and killed 80% of a 1.2 x 10(9) intravenous dose of Salmonella typhimurium after 30 min. The perfused mouse liver trapped 70% of a similar dose of S. typhimurium in a single pass, but in the perfusion model no significant killing of the trapped organisms was observed. The perfused rat liver also avidly trapped bacteria. Because of its larger size, we have been able to devise techniques to experimentally distinguish between the bacterial trapping and killing functions of this organ. When the liver was washed free of blood with sterile M-199, over 70 to 80% of a 10(6) to 10(10) dose of viable S. typhimurium was trapped after a single pass, but no significant bacterial killing was observed. When blood or plasma was added to the perfusion medium, over 50% of the trapped bacteria were killed in 15 to 30 min. Phase contrast and electron micrographs of perfused livers showed extensive extracellular trapping of bacteria in the sinusoids. Our data show that humoral factors are apparently not necessary for efficient trapping of live Salmonella by the perfused rat liver but are an absolute requirement for bacterial activity of the organ.     

Uptake and killing of Lyme disease and relapsing fever borreliae in the perfused rat liver and by isolated Kupffer cells.

In situ-perfused rat livers were infused with a single dose of 1.5 x 10(7) radiolabeled borreliae. Significant (P < 0.00005) differences in the liver uptake of the agents of Lyme borreliosis, Borrelia burgdorferi IRS, Borrelia afzelii VS461, and Borrelia garinii PBi, and that of the agents of relapsing fever, Borrelia hermsii, Borrelia parkeri, and Borrelia turicatae, were observed. The liver uptakes ranged between 65.9% for B. burgdorferi IRS and 40.5% for B. turicatae. Neither relapsing fever nor Lyme disease borreliae were recovered from infected livers when the livers were cultured in Barbour-Stoenner-Kelly II medium. The in vitro uptake of B. burgdorferi IRS by isolated rat Kupffer cells was rapid, and within 30 min of the infection, large intracellular aggregates of amorphous material were detectable by immunofluorescence with specific anti-B. burgdorferi antibody. The reculturing of B. burgdorferi IRS from Kupffer cells incubated for 24 h in RPMI medium before inoculation with bacteria was negative. The results obtained in this study indicated that borreliae are efficiently taken up and killed by rat hepatic macrophages in the absence of serum factors.     

Fungicidal activity of rabbit alveolar and peritoneal macrophages against Candida albicans.

We tested the ability of rabbit macrophages to kill Candida albicans in vitro. Resident (unstimulated) alveolar macrophages killed 28.1 +/- 1.9% of ingested organisms in 4 h, whereas resident peritoneal macrophages killed only 15.2 +/- 1.3% (mean +/- standard error of the mean, P < 0.01). Peritoneal macrophages obtained from rabbits treated 3 weeks earlier with complete Freund adjuvant showed enhanced candidacidal activity relative to normally resident peritoneal cells (28.2 +/- 3.1%, P < 0.01). Candidacidal activity by alveolar macrophages recovered from such treated animals was slightly enhanced relative to untreated alveolar macrophages (32.9 +/- 2.3%). Candidacidal activity by peritoneal and alveolar macrophages was not decreased by several agents (cyanide, azide, sulfadiazine, and phenylbutazone) that inhibit the ability of human blood monocytes to kill C. albicans. In contrast, candidacidal activity by alveolar macrophages was greatly diminished by iodoacetate, an ineffective inhibitor of this function in human monocytes. We conclude that rabbit macrophages kill C. albicans by a fungicidal mechanism distinct from the peroxidase-H2O2 mechanism of human granulocytes and monocytes, and that the fungicidal properties of peritoneal and alveolar macrophage populations are enhanced after nonspecific stimulation with complete Freund adjuvant.     

Effect of recombinant tumor necrosis factor α on in vitro amoebicidal activity of murine Kupffer cells

The present study was undertaken to determine whether recombinant tumor necrosis factor α (TNF) could induce Kupffer cells to kill Entamoeba histolytica parasite in vitro. C57BL/6 mice were used in this study. The liver was perfused and Kupffer cells harvested and treated with TNF for 6 h. It was found that Kupffer cells treated with TNF are able to kill amoebic trophozoites in vitro. These results further show that amoebicidal activity of TNF-activated Kupffer cells is dependent on the ratio of Kupffer cells to amoebic trophozoites. The maximum amoebicidal activity of Kupffer cells was observed with the ratio of one Kupffer cell to five amoebae. This study also shows that the optimal concentration of TNF is required in the induction of amoebicidal activity in Kupffer cells (10⁵ units). It seems that both oxidative-dependent and -independent mechanisms are important for the killing of amoebae by the TNF-treated Kupffer cells. It is likely that TNF-treated Kupffer cells produce endogenous TNF or other cytotoxic molecules which are capable of mediating the parasite killing. Our results indicate that the immunologic production of TNF is important in the activation of Kupffer cells to kill amoebic trophozoites.     

Effect of abrogation of natural killer cell activity on the course of candidiasis induced by intraperitoneal administration and gastrointestinal candidiasis in mice with severe combined immunodeficiency.

Candida albicans CFU per gram of tissue recovered from livers, spleens, and kidneys of 12 severe combined immunodeficiency (scid) and 12 BALB/c mice 5 days after intraperitoneal (i.p.) administration of 10(7) C. albicans cells were not significantly different. Nine scid mice given normal rabbit serum (NRS) as a control and eight scid mice given anti-asialo-GM1 (alpha-ASGM1) had C. albicans CFU per gram recovered from livers and spleens 1 week after i.p. administration of C. albicans that were not significantly different, despite virtual elimination of natural killer (NK) cell activity in mice treated with alpha-ASGM1. At 2 weeks after i.p. administration, despite significantly increased NK cell activity in eight infected NRS-treated scid mice and virtual elimination of NK cell activity by alpha-ASGM1 treatment of eight scid mice, C. albicans CFU per gram recovered from livers and kidneys were not significantly different. At 2 weeks after intragastric administration of 2 x 10(6) C. albicans cells, eight NRS- and eight alpha-ASGM1-treated scid mice had identical proportions colonized with C. albicans and similar C. albicans CFU per gram recovered from feces. There was no evidence of hematogenous dissemination in either group. Similar results were seen 1 week after intragastric administration of 10(7) C. albicans cells. We conclude that NK cell activity is increased by i.p. administration of C. albicans in scid mice, but nontheless, abrogation of NK cell activity is not associated with enhanced susceptibility to candidiasis induced by i.p. administration and also is not associated with enhanced susceptibility to gastrointestinal colonization or hematogenous dissemination after intragastric administration of C. albicans.     

Enhanced Phagocytosis and Bactericidal Activity of Hepatic Reticuloendothelial System During Endotoxin Tolerance

The effects of tolerance to Escherichia coli endotoxin on the phagocytic and bactericidal activity of the hepatic reticuloendothelial system against viable E. coli were examined using ex vivo perfused rat livers. Livers were isolated from control and endotoxin-tolerant rats and perfused with a medium containing 5% homologous serum from either control or tolerant rats. After the addition of the E. coli (2 × 10⁷ cells per ml) to the perfusate, the hepatic clearance of the bacteria was followed for 30 min. The highest activation of the hepatic reticuloendothelial system was observed when serum from tolerant animals was added to the perfusate. Under these conditions phagocytosis was 47% (12% in controls), and 37 to 38% of the bacteria were killed (5% in controls). This activation was less when livers obtained from tolerant rats were perfused with serum from controls or with saline only. The data suggests that, during endotoxin tolerance, humoral factors play an important role in the activation of the hepatic reticulendothelial system, although a direct stimulation of Kupffer cells also occurs. The enhancement of phagocytosis by tolerant serum did not require the presence of homologous antibodies and involved the activation of the alternative complement pathway, since it was lost after removal of factor B activity. On the other hand, stimulation of intracellular killing required both complement and specific antibodies. The data suggest a role of endotoxin in the activation of humoral and cellular mechanisms involved in the host resistance to gram-negative bacterial infection.     

Candidacidal mechanisms of peritoneal macrophages activated with lymphokines or gamma-interferon

The mechanisms by which resident peritoneal macrophages, activated in vitro by lymphokines (LK) or recombinant gamma-interferon (IFN), kill Candida parapsilosis or C. albicans were studied. Resident non-activated peritoneal macrophages killed C. parapsilosis (55.5% SD 6.8%), but not C. albicans. This killing was completely inhibited by superoxide dismutase (SOD), partially by dimethyl sulphoxide (DMSO), but not by catalase or azide. Killing correlated with a brisk lucigenin-dependent chemiluminescence (CL) response by macrophages interacting with C. parapsilosis. No enhanced luminol-dependent CL response was observed in this system. This suggests that C. parapsilosis is killed by resident macrophages via a mechanism dependent on the presence of superoxide anion. By contrast, killing of C. parapsilosis by activated macrophages (49.0% SD 5.9%) was not inhibited by SOD or DMSO, suggesting the induction of a non-oxidative candidacidal mechanism. C. albicans was killed only by macrophages activated with IFN (52.0% SD 3.7%) or LK (55.7% SD 2.8%). Inhibition of killing by SOD was greater in IFN- than in LK-activated macrophages. Conversely, killing by LK-, but not IFN-, activated macrophages was significantly inhibited by catalase, DMSO or azide. The killing by LK-activated macrophages, and its inhibition by scavengers, correlated with the luminol-dependent CL response. The non-killing resident macrophages interacting with C. albicans made lucigenin-dependent CL responses similar to those of activated macrophages. The mechanisms enabling killing of C. albicans induced by activation appear to be different for LK and IFN, and appear to depend upon the myeloperoxidase systems and superoxide respectively.     

Opsonic requirements for hepatic clearance of pneumococci

An in situ isolated, perfused rat liver system was used to evaluate various opsonins for hepatic trapping and killing of encapsulated, virulent, type 3 pneumococci. Pneumococci were rapidly trapped in the liver in the presence of all potential opsonins including Hanks balanced salt solution with added colloid. However, with some of the potential opsonins the organisms remained viable and could be recovered from the liver. With others there was killing of pneumococci. The combination of rat antibody and complement was effective as an opsonin and produced about the same degree of killing as the same human components. When tested separately killing was not promoted by rat complement, human complement, or human antibody. However, when ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid-Mg2+ was added to block the classical pathway and preserve the alternative pathway there was significant pneumococcal killing which may have been complement mediated or due to an adverse effect of ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid-Mg2+ on the organisms. Fibronectin and C-reactive protein reduced the number of surviving microorganisms, although the change was not significant. Immunoglobulin G (IgG)-IgM, IgG, or IgM with complement, and antibody + the classical complement pathway, significantly reduced survival of the organisms. The best killing occurred with antibody plus complement plus fibronectin, which reduced mean survival to 24% during the 1-h perfusion.     

Systemic candidosis in silica-treated athymic and euthymic mice.

Intravenous silica injections were used to assess the role of macrophages in the resistance of BALB/c nude and euthymic mice to systemic candidosis. CFU of Candida albicans in the kidneys, livers, and spleens of saline- or silica-treated mice were enumerated at various times after inoculation with 10(4) viable yeast cells. The number of C. albicans organisms recovered from the kidneys of silica-treated euthymic mice was similar to the number recovered from saline-treated controls during the first 3 days of infection; however, at every assay period thereafter, the number of organisms recovered from the kidneys of silica-treated mice was dramatically reduced (100- to 1,000-fold). Conversely, silica-treated nude mice were no more susceptible to systemic candidosis than were saline-injected nude mice. Silica treatment did not alter the ability of treated or control mice to clear C. albicans from the liver and spleen. These results demonstrate that macrophages play an important role in susceptibility to Candida infections.     

Activation of pulmonary macrophages for fungicidal activity by gamma-interferon or lymphokines.

The ability of murine recombinant gamma interferon (IFN) or lymphokines to enhance the fungicidal activity of murine pulmonary macrophages (PuM) was studied in in vitro. PuM monolayers were incubated overnight with IFN, lymph node cells (LNC) plus concanavalin A, supernatants from Con A stimulated LNC or spleen cell cultures (Con A Sup), or tissue culture medium (TCM) +/- Con A (5 micrograms/ml) or +/- lipopolysaccharide (LPS, 10 ng to 10 micrograms/ml). After treatment, culture fluids were removed and PuM were challenged for 4 h with the yeast-form Blastomyces dermatitidis or 2 h with Candida albicans. Inoculum colony forming units (CFU) of B. dermatitidis were significantly reduced by PuM treated with 1000 U/ml of IFN (25 +/- 3%), Con A Sup (25 +/- 3%) or LNC plus Con A (37-44%), but not by TCM, ConA or LPS. Candida albicans was killed by PuM treated with Con A Sup (33 +/- 8%) or LNC plus Con A (30-43%), but not by TCM, Con A, or LPS, and the activity of Con A Sup was neutralized by anti-IFN antibody. Candida albicans was not significantly killed by PuM treated with IFN doses ranging from 1 to 10(5) U/ml; nor did addition of LPS to IFN, or prolonged (3 day) treatment with IFN, result in significant killing of C. albicans by PuM. However, IFN (100 U/ml) could activate resident peritoneal macrophages for significant candidacidal activity (63%). These data indicate that PuM can be activated for fungicidal activity, and that PuM differ from resident peritoneal macrophages with regard to induction of candidacidal activity by recombinant gamma-IFN.     

Role of activated macrophages in resistance to systemic candidosis

To evaluate further the contribution of activated macrophages in resistance, the course of systemic candidosis was assayed in beige and NLM mice that had been previously infected with Mycobacterium bovis (BCG). Four weeks following BCG infection, mice were inoculated intravenously with 1 x 10(4) viable Candida albicans. At various times thereafter, the number of C. albicans colony-forming units in the livers, spleens, and kidneys was determined. The average number of CFU recovered from the kidneys of NLM mice decreased throughout the assay and was comparable in both BCG-treated and control mice. In contrast, the number of CFU cultured from the kidneys of untreated control beige mice progressively increased throughout the assay period. This profile of renal susceptibility was not appreciably altered in BCG-treated beige mice. However, fewer (10- to 100-fold) CFU were cultured from the livers and spleens of BCG-treated beige and NLM mice than from untreated controls. These results support the hypothesis that in the absence of functional polymorphonuclear leukocytes, activated macrophages represent a means to control the proliferation of C. albicans.     

Killing of Coccidioides immitis by human peripheral blood mononuclear cells.

The ability of human peripheral blood mononuclear cells (MNL) obtained from healthy donors to kill the fungus Coccidioides immitis was examined in vitro with an assay that uses a single fungal particle per well. MNL killed 25.0% +/- 3.5% of a coccidioidal arthroconidial target, compared with the 4.7% +/- 2.9% killed by polymorphonuclear leukocytes obtained from the same donors (P = 0.012). Arthroconidial killing by MNL was not dependent on donor delayed dermal hypersensitivity to spherulin. Killing of another fungal target, Candida glabrata, was not significantly different between MNL and polymorphonuclear leukocytes (P = 0.783). Depletion of monocytes from MNL with Sephadex G-10 resulted in a significant reduction in arthroconidial killing (21.4% +/- 13.6% versus 2.4% +/- 3.4%; P = 0.025), while enrichment of monocytes by Percoll density gradient centrifugation or plastic adherence resulted in significantly increased arthroconidial killing compared with that by MNL (P = 0.005 and 0.001, respectively). Killing of 96-h spherules by MNL was 7.3% +/- 3.1%, significantly less than the 21.4% +/- 2.8% killing of arthroconidia in the same experiments (P = 0.016). Incubation of MNL with human recombinant gamma interferon or tumor necrosis factor alpha did not result in increased MNL killing of coccidioidal arthroconidia under various conditions. These results suggest that MNL have an inherent ability to kill coccidioidal arthroconidia in vitro which is not dependent on prior host exposure to C. immitis. This activity appears to reside in peripheral blood monocytes.     

Influence of C-phycocyanin on hepatocellular parameters related to liver oxidative stress and Kupffer cell functioning

OBJECTIVES: Kupffer cells, liver macrophages involved in immunomodulation, phagocytosis, and biochemical attack, can induce cytotoxicity and inflammation when their activity is exacerbated. The aim of this study was to evaluate the effects of C-phycocyanin on Kupffer cell functioning considering its antioxidant and anti-inflammatory properties. MATERIALS AND METHODS: Actions of C-phycocyanin on colloidal carbon phagocytosis, carbon-induced respiratory burst activity, and sinusoidal lactate dehydrogenase (LDH) release were studied in isolated perfused mouse liver. The influence of C-phycocyanin on tumor necrosis factor-a (TNF-alpha) and nitrite levels in serum and liver nitric oxide synthase (NOS) activity was assessed in rats subjected to thyroid hormone (T3) administration, a condition known to underlie hepatic oxidative stress comprising an increased Kupffer cell activity. RESULTS: C-phycocyanin elicited a concentration-dependent inhibition of carbon phagocytosis and carbon-induced O2 uptake (IC50 = 0.2 mg/ml) by perfused livers, with a 52% diminution in the carbon-induced sinusoidal release of LDH being found at a concentration of 0.25 mg/ml. Thyroid calorigenesis induced an 82-fold increase in serum TNF-alpha levels, an effect that was suppressed by pretreatment with C-phycocyanin, the antioxidant alpha-tocopherol, and by the Kupffer cell inactivator gadolinium chloride. C-phycocyanin also suppressed the T3-induced increases in serum nitrite levels (234%) and in the activity of hepatic NOS (75%). CONCLUSIONS: C-phycocyanin significantly decreases Kupffer cell phagocytosis and the associated respiratory burst activity, effects that may contribute to the abolition of oxidative stress-induced TNF-alpha response and NO production by hyperthyroid state.     

Correlation of susceptibility of immature mice to fungal infection (blastomycosis) and effector cell function

Immature mice are highly susceptible to blastomycosis, which is similar to other mycoses and has parallels in humans. The murine susceptibility is noteworthy in that it persists beyond the development of resistance to other, nonfungal pathogens and the maturation of most immune functions. As the susceptibility to blastomycosis appeared to be related to an early event after infection, primary effector cell function was studied. We found that peritoneal inflammatory cells, enriched for neutrophils, from immature (3-week-old) mice killed nonphagocytizable Blastomyces dermatitidis cells less (25%) than did cells from mature (8-week) mice (70%) (P<0.01), a defect intrinsic to the neutrophils. This correlated with an impaired immature cell oxidative burst. Killing of phagocytizable Candida albicans was not significantly different, 73 versus 87%. Thioglycolate-elicited cells were more impaired; killing of B. dermatitidis was insignificant, and killing of C. albicans was more impaired in immature (16% killing) than in mature (45%) cells (P<0.02). Peripheral blood neutrophils from mature animals killed B. dermatitidis (41%) more than did those from immature animals (10%) (P<0.02); C. albicans was killed efficiently by both. Resting or activated peritoneal macrophages from both types of animals showed no differences in B. dermatitidis killing. These results suggest that the susceptibility of immature mice is related at least in part to the depressed capacity of their neutrophils to kill B. dermatitidis.     

Antifungal activity of splenic, liver and pulmonary macrophages against Candida albicans and effects of macrophage colony-stimulating factor.

Disseminated infections due to Candida albicans are frequently encountered in immunocompromised patients. We compared the antifungal activities of macrophages residing in spleen, liver and lungs of rabbits against blastoconidia and pseudohyphae of C. albicans. Splenic adherent cells (SAC), Kupffer cells (KC) and pulmonary alveolar macrophages (PAM) all ingested blastoconidia efficiently. SAC caused significantly more damage to unopsonized pseudohyphae compared with KC (P < 0.01) or PAM (P < 0.001). Incubation of SAC with 15 ng ml(-1) of recombinant human macrophage colony-stimulating factor (M-CSF) at 37 degrees C for 2 days significantly enhanced phagocytosis (P = 0.02) and killing (P = 0.05) of blastoconidia. In contrast, M-CSF had no effect on phagocytic activities of KC or PAM against blastoconidia or on damage caused by any of the macrophages to pseudohyphae of C. albicans. Thus, although all three resident macrophage types ingest blastoconidia efficiently, they differ in their capacity to cause damage to pseudohyphae and in their responsiveness to M-CSF for antifungal activation. M-CSF augments the capacity of SAC to ingest and kill blastoconidia and may therefore have a role in the treatment and prevention of hematogenously disseminated candidiasis.