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Biomedical subjects

G B Toews

Publications and source records attributed to G B Toews.

At least 37 records · Page 2Linked to original sources
PubMed1999

Cutting edge: Role of C-C chemokine receptor 5 in organ-specific and innate immunity to Cryptococcus neoformans.

After intratracheal inoculation of the AIDS-associated pathogen Cryptococcus neoformans, 12-wk survival was >90% for CCR5+/+ mice but <25% for CCR5-/- mice. There were no defects in lung leukocyte recruitment (wk 5), pulmonary clearance, or delayed-type hypersensitivity in CCR5-/- mice. However, CCR5-/- mice had defects in leukocyte recruitment into the brain and, strikingly, in elimination of cryptococcal polysaccharide from the brain. In nonimmune CCR5-/- mice, there was a significant defect in macrophage recruitment after challenge with shed cryptococcal products (C. neoformans filtrate Ag) but not other nonspecific stimuli. Thus, CCR5 plays specific roles in innate immunity and organ-specific leukocyte trafficking during host defense against C. neoformans.

Animals↗
PubMed1999

Induction of lung fibrosis in the mouse by intratracheal instillation of fluorescein isothiocyanate is not T-cell-dependent.

Pulmonary fibrosis is the pathological result of a diverse group of insults. Common features of this group of diseases include chronic inflammation and immune cell activation. The pathogenesis of pulmonary fibrosis is not well defined and the prognosis is poor, highlighting the need for good animal models to elucidate the cellular and molecular events that lead to pulmonary fibrosis. This paper provides insight on a newly described model of pulmonary fibrosis using a single intratracheal challenge with fluorescein isothiocyanate (FITC). Balb-c and C57BL6 mice given intratracheal FITC develop acute lung injury followed by chronic inflammation. Significant increases in lung collagen content compared to saline-treated mice are noted at day 21 after inoculation. T-cell-deficient animals develop similar increases in lung collagen content compared to immunocompetent controls despite the abrogation of specific anti-FITC serum antibodies. Thus, the induction of fibrosis in FITC-challenged mice is not dependent on T cell immunity. Persistent chronic inflammation and acute lung injury may be the inciting events for the development of lung fibrosis in this model.

Animals↗
PubMed1999

Phenotypic and functional characterization of normal rat pleural macrophages in comparison with autologous peritoneal and alveolar macrophages.

Pleural mononuclear phagocytes (PleMP) were isolated from normal rats by pleural lavage and compared with autologous peritoneal (PerMP) and bronchoalveolar mononuclear phagocytes (BAMP) isolated by peritoneal and bronchoalveolar lavage, respectively. The phagocytic activity of PleMP, PerMP, and BAMP, evaluated by testing their ability to ingest latex beads, was lower for PleMP and PerMP than for BAMP. The phenotype of PleMP, PerMP, and BAMP was characterized by immunocytochemical staining with a panel of monoclonal antibodies (mAbs). As expected, PleMP, PerMP, and BAMP did not react with OX19, OX33, ED5, MOM/3F12/F2, and anticytokeratin mAbs, specific for T lymphocytes, B lymphocytes, dendritic cells, granulocytes, and epithelial/mesothelial cells, respectively. Moreover, PleMP and PerMP populations were highly enriched with OX6-, OX42-, ED7-, and ED8-positive MP, whereas BAMP population was enriched with ED1- and ED9-positive cells. To test the ability of PleMP, PerMP, and BAMP to function as accessory cells (AC), mitomycin C-treated MP were used as stimulatory cells in mixed leukocyte reaction experiments, using allogeneic T cells as responders. 3HdTR incorporation by T cells was assessed as an index of AC function. PleMP and PerMP were more potent AC than BAMP. Moreover, when cultured together with autologous pulmonary interstitial dendritic cells, PleMP and PerMP exerted a more potent ability to stimulate T-cell proliferation than did BAMP. To investigate the capacity of MP to function as bactericidal and fungicidal cells, we tested their ability to kill Escherichia coli and Cryptococcus neoformans, respectively. PleMP and PerMP were less potent bactericidal and fungicidal cells than BAMP. The results of this study demonstrate that PleMP isolated from normal rat pleural space are functionally and phenotypically different from BAMP but similar to PerMP, and suggest that these cells might play an important role in cell-mediated immune reactions in the pleural space.

Animals↗
PubMed1998

Idiopathic pulmonary fibrosis: predicting response to therapy and survival.

Idiopathic pulmonary fibrosis (IPF) is associated with significant morbidity and mortality despite aggressive therapy. Thirty-eight patients with biopsy-proven IPF were studied to identify pretreatment features that could be used to predict short-term improvement in pulmonary function and improved longer term survival. In all patients, a pretreatment clinical (dyspnea), radiographic (chest radiograph), and physiologic (pulmonary function including exercise saturation) score was generated (CRP). A high-resolution CT scan (HRCT) was independently scored by four radiologists for ground glass (CT-alv) and linear opacity (CT-fib) on a scale of 0-4. Open lung biopsy samples were scored for cellular infiltration, interstitial fibrosis, desquamation, and granulation by an experienced pulmonary pathologist. All patients were treated with 3 mo of high-dose steroids and the CRP scoring repeated. Patients were divided into three groups: responders with a greater than 10-point drop in CRP (n = 10); stable with +/- 10 point change in CRP (n = 14); and nonresponders with > 10 point rise in CRP or death (n = 14). Those responding to steroids were treated for 18 mo in a tapering fashion. In all others, steroids were tapered quickly and oral cyclophosphamide prescribed. Responders (10 of 38) had a lower age (45.1+/-4.3 yr) than nonresponders (61.4+/-3.5 yr) or those remaining stable (53.1+/-3.3 yr) (p = 0.01). Pretreatment CRP was higher in responders (58.8+/-5.6) than nonresponders (40.5+/-4.7) or stable individuals (37.6+/-4.7) (p = 0.01). Cellular infiltration score of the open lung biopsies was higher in responders (7.6+/-0.6) than stable individuals (5.7+/-0.5) (p = 0.04). The CT-alv scores were higher and CT-fib scores were lower in responders than nonresponders. Receiver operating curve (ROC) analysis was employed to identify pretreatment features of longer term survival (follow-up of 29.1+/-2.3 mo). Only CT-fib (p = 0.009) and pathology fibrosis score (p = 0.03) were able to predict mortality. A pretreatment CT-fib score > or = 2.0 demonstrated 80% sensitivity and 85% specificity in predicting survival. Those patients who did not respond to initial steroid therapy demonstrated a worse long-term survival and greater likelihood of decreased pulmonary function. We demonstrate that pretherapy pulmonary function, pathologic and radiographic parameters are different in individuals who respond to initial prednisone therapy. Only HRCT imaging and pathologic fibrosis were able to reliably predict long-term survival in patients with biopsy-proven IPF.

Adult↗
PubMed1997

Macrophage inflammatory protein-1alpha (MIP-1alpha) is required for the efferent phase of pulmonary cell-mediated immunity to a Cryptococcus neoformans infection.

Our objective was to define the role of the chemokine macrophage-inflammatory protein-1alpha (MIP-1alpha) in the efferent phase of pulmonary cell-mediated immunity (CMI) against Cryptococcus neoformans. Following intratracheal inoculation of C. neoformans (24067) into CBA/J mice, the development of CMI was required for leukocyte recruitment into the lungs at 2 wk postinfection. MIP-1alpha mRNA was expressed by day 6 postinfection, and MIP-1alpha protein in bronchoalveolar lavage fluid was detectable at day 6, but significantly elevated at days 19 and 33. Administration of neutralizing anti-MIP-1alpha Abs from days 7 to 13 blocked the increase in bronchoalveolar lavage fluid MIP-1alpha and resulted in a 37% decrease in total leukocytes in the lungs at day 16. There were 66% fewer macrophages/monocytes and 42% fewer neutrophils in the lungs of anti-MIP-1alpha-treated mice, and the pulmonary burden of C. neoformans was threefold higher. There was no significant difference in the number of eosinophils, CD4+, CD8+, or B220+ lymphocytes between the two groups of mice. Neutralization of MIP-1alpha did not significantly decrease the levels of monocyte chemotactic protein-1 (MCP-1); however, neutralization of MCP-1 significantly decreased MIP-1alpha levels, demonstrating that induction of MIP-1alpha was largely dependent on MCP-1 production. Neutralization of MIP-1alpha also blocked the cellular recruitment phase of a recall response to cryptococcal Ag in the lungs of immunized mice. Thus, in both the contexts of active cryptococcal infection or rechallenge with cryptococcal Ag, MIP-1alpha was required during the efferent phase of CMI for maximal leukocyte recruitment into the lungs, most notably the recruitment of phagocytic effector cells (neutrophils and macrophages).

Animals↗
PubMed1997

Alveolar macrophages are required for protective pulmonary defenses in murine Klebsiella pneumonia: elimination of alveolar macrophages increases neutrophil recruitment but decreases bacterial clearance and survival.

To study the in vivo role of alveolar macrophages (AM) in gram-negative bacterial pneumonia in mice, AM were eliminated by the intratracheal (i.t.) administration of dichloromethylene diphosphonate encapsulated liposomes. Subsequently, the AM-depleted mice were infected i.t. with 100 CFU of Klebsiella pneumoniae, and the effects of AM depletion on survival, bacterial clearance, and neutrophil (polymorphonuclear leukocyte [PMN]) recruitment were assessed. It was shown that depletion of AM decreases survival dramatically, with 100% lethality at day 3 postinfection, versus 100% long-term survival in the control group. This increased mortality was accompanied by 20- to 27- and 3- to 10-fold increases in the number of K. pneumoniae CFU in lung and plasma, respectively, compared to those in nondepleted animals. This decreased bacterial clearance was not due to an impaired PMN recruitment; on the contrary, the K. pneumoniae-induced PMN recruitment in AM-depleted lungs was sevenfold greater 48 h postinfection than that in control infected lungs. Together with an increased PMN infiltration, 3- and 10-fold increases in lung homogenate tumor necrosis factor alpha (TNF-alpha) and macrophage inflammatory protein 2 (MIP-2) levels, respectively, were measured. Neutralization of TNF-alpha or MIP-2, 2 h before infection, reduced the numbers of infiltrating PMN by 41.6 and 64.2%, respectively, indicating that these cytokines mediate PMN influx in infected lungs, rather then just being produced by the recruited PMN themselves. Our studies demonstrate, for the first time, the relative importance of the AM in the containment and clearance of bacteria in the setting of Klebsiella pneumonia.

Animals↗
PubMed1997

Dendritic cells with a potent accessory activity are present in human exudative malignant pleural effusions.

Dendritic cells are human leucocyte antigen (HLA)-DR positive accessory cells, that play a critical role in the development of cell-mediated immune reactions. Since the pleural space is frequently involved in cell-mediated immune reactions, we sought to isolate dendritic cells from pleural fluid. Pleural effusion mononuclear cells (PEMCs) were obtained by Ficoll centrifugation of exudative pleural effusions recovered from 19 patients with malignant pleurisy. After double-step adherence, firmly-adherent mononuclear cells (FAMs) and loosely-adherent mononuclear cells (LAMs) were recovered. The latter cells were centrifuged on a bovine plasma albumin gradient to obtain a loosely-adherent low density fraction. Nonadherent cells were rosetted with sheep red blood cells (SRBC) to obtain a nonadherent nonrosetting (NANR) cell fraction. Mitomycin C-treated PEMCs, NANRs, FAMs, and LAMs served as stimulatory cells in mixed leucocyte reaction experiments. 3H-thymidine incorporation by purified normal allogeneic blood T-lymphocytes was assessed as an index of accessory cell function. The phenotype of NANR, FAM and LAM cells was characterized using single and double stainings with a panel of monoclonal antibodies (MoAbs). Accessory cell (AC) activity (counts per minute (cpm) x 10(3)(+/-SE); 2.5 x 10(4) AC x well(-1) of LAM (148+/-24) and NANR (108.4+/-11.2) was greater than that observed for FAM (59.3+/-9.4) and for unfractioned PEMC (13.8+/-4.9). The FAM fraction was virtually entirely composed of CD68+ HLA-DR+ mononuclear phagocytes. NANR and LAM contained 51+/-12% and 65+/-6% HLA-DR+ cells, respectively, and most HLA-DR positive cells were negative for CD3, CD19, and CD68, markers for T-, B-lymphocytes and mononuclear phagocytes. Moreover, both NANR and LAM fractions contained significant numbers of cells bearing the RFD1 surface marker, expressed on dendritic cells. These results suggest that dendritic cells are present in exudative pleural effusions, and that they may be involved in the development of cell-mediated immune reactions in the pleural space.

Aged↗
PubMed1996

Afferent phase production of TNF-alpha is required for the development of protective T cell immunity to Cryptococcus neoformans.

The development of T cell immunity is required to clear a pulmonary Cryptococcus neoformans infection (via the recruitment and activation of inflammatory cells). The objective of our studies was to determine whether TNF-alpha is required during the afferent phase of the response. The levels of TNF-alpha mRNA and protein in the lungs increased following intratracheal inoculation of CBA/J mice with C. neoformans 52 and preceded the development of an inflammatory response in the lungs. Administration of neutralizing TNF-alpha-specific antiserum on days 0, 3, 6, and 9 reduced inflammatory cell recruitment by 80% on day 13, resulting in a 3-fold increase in lung C. neoformans CFU. The number of CD4+ T cells was decreased by 65%, the number of neutrophils was decreased by 84%, and the number of macrophages was decreased by >98%. Strikingly, a single dose of neutralizing anti-TNF-alpha serum was sufficient to prevent the development of protective cell-mediated immunity on day 35 if administered on day 0, but was ineffective if delayed until day 14. Day 0 anti-TNF-alpha-treated mice could not generate cryptococcus-specific delayed type hypersensitivity reactivity, clear the infection from their lungs (10(4)-fold increase in CFU), control dissemination to the spleen and brain (10(5)- and 10(6)-fold increases in CFU), or adoptively transfer cryptococcus-specific immunity (mononuclear cell recruitment into the lungs following intratracheal challenge or footpad delayed type hypersensitivity). Thus, the production of TNF-alpha during the afferent phase of the immune response against a pulmonary C. neoformans infection (before day 14) is critical for the development of protective T cell immunity in both the lungs and extrapulmonary sites.

Animals↗
PubMed1996

Urokinase is required for the pulmonary inflammatory response to Cryptococcus neoformans. A murine transgenic model.

Urokinase (uPA) is hypothesized to provide proteolytic activity enabling inflammatory cells to traverse tissues during recruitment, and it is implicated as a cytokine modulator. Definitive evaluation of these hypotheses in vivo has previously been impossible because uPA could not completely and irreversibly be eliminated. This limitation has been overcome through the development of uPA-deficient transgenic mice (uPA-/-). Using these mice, we evaluated the importance of uPA in the pulmonary inflammatory response to Cryptococcus neoformans (strain 52D). C. neoformans was inoculated into uPA-/- and control mice (uPA+/+), and cell recruitment to the lungs was quantitated. The number of CFU in lung, spleen and brain was determined to assess clearance, and survival curves were generated. By day 21 after inoculation, uPA-/- mice had markedly fewer pulmonary inflammatory (CD45+), CD4+, and CD11b/CD18+ cells compared with uPA+/+ controls (P<0.0007); pulmonary CFUs in the uPA-/- mice continued to increase, whereas CFUs diminished in uPA+/+ mice(P<0.005). In survival studies, only 3/19 uPA+/+ mice died, whereas 15/19 uPA-/- mice died (p<0.001). We have demonstrated that uPA is required for a pulmonary inflammatory response to C. neoformans. Lack of uPA results in inadequate cellular recruitment, uncontrolled infection, and death.

Animals↗
PubMed1996

Granulocyte-macrophage colony-stimulating factor overrides the immunosuppressive function of corticosteroids on rat pulmonary dendritic cells.

Pulmonary dendritic cells (DC) are present in extremely small numbers, but they are the most potent antigen-presenting cells in the lungs. Pure populations of DC can be isolated from the lung following collagen digestion, Percoll gradient centrifugation, removal of phagocytic cells and flow cytometric sorting for cells which exhibit high levels of surface major histocompatibility complex (MHC) class II molecules. Exogenous GM-CSF enhances this immunostimulatory capacity of the pulmonary DC. Soluble factors produced by type II airway epithelial cells and interstitial macrophages also enhance the immunostimulating capacity of pulmonary DC while alveolar macrophages suppress it. Thus, the function of DC may be regulated by locally produced cytokines. Corticosteroids are widely used as immunosuppressive agents in pharmacotherapy. While these agents are known to inhibit T cell proliferation and macrophage activation, their effects on DC are not known. We found that dexamethasone (Dex) pretreatment resulted in about a 50% reduction in the immunostimulatory capacity of rat pulmonary DC. This was associated with downregulation of MHC class II (Ia) expression. Dex-induced suppression of DC function could be restored with GM-CSF. We conclude that corticosteroids downregulate antigen-presenting capacity by direct suppression of pulmonary DC. This immunosuppressive effect of corticosteroids on DC may, however, be abrogated by exogenous GM-CSF. Corticosteroids and GM-CSF are therapeutic agents with potent direct immunomodulating effects on DC.

Adrenal Cortex Hormones↗
PubMed1995

The role of monocyte chemotactic protein-1 (MCP-1) in the recruitment of monocytes and CD4+ T cells during a pulmonary Cryptococcus neoformans infection.

Cryptococcus neoformans is acquired via the respiratory tract and is the leading cause of fatal mycosis in AIDS. Development of a T cell-mediated pulmonary inflammatory response is critical for clearance of this pathogen; however, the chemotactic factors that mediate inflammatory cell recruitment into the lungs have not been identified. In the present study, the bronchoalveolar lavage (BAL) fluid levels of the C-C chemokine monocyte chemotactic protein-1 (MCP-1) and the recruitment of inflammatory cells both increased following pulmonary infection with C. neoformans. The kinetics of MCP-1 production in the lungs correlated most closely with the recruitment of CD4+ T cells and monocytes/macrophages. Administration of neutralizing anti-MCP-1 Abs in vivo reduced the BAL fluid levels of MCP-1, decreased the recruitment of both macrophages (> 95%) and CD4+ T cells (76 +/- 9%), and inhibited cryptococcal clearance. Although no in vitro neutrophil or B cell chemotactic activity has been reported for MCP-1, recruitment of these leukocytes was also decreased in anti-MCP-1-treated mice (most likely an indirect effect of reducing the number of CD4+ T cells and macrophages). Neutralization of MCP-1 also resulted in decreased BAL fluid levels of TNF-alpha and IL-6. This is the first demonstration of a role for MCP-1 in clearance of an infection, and provides direct evidence that MCP-1 plays a critical role in the T cell-dependent immune response to C. neoformans.

Animals↗
PubMed1995

Down-regulation of the afferent phase of T cell-mediated pulmonary inflammation and immunity by a high melanin-producing strain of Cryptococcus neoformans.

The interaction(s) between cryptococcal virulence factors and leukocytes involved in generating protective cell-mediated immunity is not well defined. Intratracheal inoculation of Cryptococcus neoformans strain 52 induced a vigorous T cell-mediated pulmonary inflammatory response that controlled the growth of the organism. In contrast, strain 145 induced a pulmonary inflammatory response that was delayed in onset, slower to develop, and ineffective in controlling the infection. In addition, the expansion of cryptococcus-specific lymphocytes in the pulmonary lymph nodes and titer of specific Abs in the serum of strain 145-infected mice were both diminished markedly. Of the known cryptococcal virulence factors, these two strains differed only in melanin production (52-low and 145-high). Heat-killed strain 145 cryptococci (HKC-145) that had been rendered melanin-negative induced TNF-alpha production by alveolar macrophages in vitro and stimulated vigorous cryptococcus-specific lymphoproliferation. In contrast, high melanin-containing HKC-145 inhibited TNF-alpha production and lymphoproliferation. In vivo, mice infected with melanin low strain 52, but not melanin high strain 145, had elevated levels of TNF-alpha in the bronchoalveolar lavage fluid. Mice co-infected with strains 145 and 52 generated a pulmonary inflammatory response resulting in increased long-term survival. Taken together, these studies demonstrate that melanin does not protect cryptococci from being eliminated in vivo by recruited, activated effector cells; but melanin can inhibit the recognition of the organism by host defenses, thereby down-regulating the afferent phase of T cell-mediated immunity, e.g., TNF-alpha production and lymphoproliferation.

Animals↗
PubMed1995

Influence of sample number and biopsy site on the histologic diagnosis of diffuse lung disease.

BACKGROUND: Although open biopsy is considered the optimal method for obtaining lung tissue for the diagnosis of diffuse infiltrative pulmonary disorders, there are no universally established guidelines concerning biopsy site selection and the ideal number of tissue samples. Relatively few investigations have been devoted to the influence exerted by the site and number of biopsy samples on the histologic diagnosis. METHODS: Seventy-seven open biopsy samples obtained from different lobes of 28 patients with idiopathic pulmonary fibrosis were analyzed. The histopathologic features were evaluated semiquantitatively and the results from each sample compared with those of the other samples obtained from each patient. RESULTS: Statistically significant differences in histopathologic features were not observed between samples. CONCLUSIONS: A single generous (2 cm or greater diameter) sample, obtained from a representative region of the radiographically most involved lobe, will suffice for diagnostic and evaluation purposes.

Adult↗
PubMed1995

Regulation of rat pulmonary dendritic cell immunostimulatory activity by alveolar epithelial cell-derived granulocyte macrophage colony-stimulating factor.

The presentation and recognition of foreign antigen is the critical initial event in the development of local immunity. In the lung, antigen-presenting cell activity is largely attributable to pulmonary dendritic cells (DC) that are distributed along the airways and throughout the pulmonary interstitium in close proximity to overlying alveolar epithelial cells. To test the hypothesis that DC immunostimulatory activity might be locally regulated by overlying alveolar epithelial cells, we evaluated the ability of rat type II alveolar epithelial cells to influence the capacity of purified rat pulmonary DC to stimulate T-cell proliferation in an allogeneic, mixed leukocyte reaction. We found that alveolar epithelial cells greatly enhanced the ability of dendritic cells to induce T-cell proliferation. This effect on DC immunostimulatory activity was mediated by a soluble factor preferentially secreted from the basolateral epithelial cell surface. Alveolar epithelial cultures were found to express mRNA for granulocyte macrophage colony-stimulating factor (GM-CSF), and blocking antibodies against GM-CSF partially neutralized the effect of epithelial cell-conditioned media on DC stimulatory activity, indicating that the effect was due at least in part to alveolar epithelial cell-derived GM-CSF. Through the polar secretion of GM-CSF, alveolar epithelial cells may play an important role in creating distinct immunologic environments within the lung.

Animals↗
PubMed1994

CD8 cells play a critical role in delayed type hypersensitivity to intact Cryptococcus neoformans.

Although cell-mediated immunity is critical for optimal host defense to C. neoformans, the role of T lymphocyte subsets is complex and poorly understood. CD8 cells are important both for optimal host defense against C. neoformans, and for expression of delayed type hypersensitivity (DTH). Because host defense correlates with the ability to mount a DTH response to C. neoformans, the current studies were performed to determine the mechanism by which CD8 cells participate in DTH. Mice were immunized by the intratracheal route with live C. neoformans, or by the subcutaneous route with heat-killed C. neoformans. Mice were depleted of CD8 cells in vivo by administration of mAb. After challenge with soluble cryptococcal Ag, the DTH response was quantified as footpad swelling. We found that mice depleted of CD8 cells before immunization were unable to express DTH. Mice depleted of CD8 cells after immunization but before challenge also were unable to express DTH. Splenocytes of mice depleted of CD8 cells in vivo, before immunization, failed to transfer DTH to naive, undepleted mice. Immune splenocytes depleted of CD8 cells in vitro also failed to transfer DTH to naive, undepleted mice. These data indicate that CD8 cells were necessary during the challenge and immunizing phases of DTH, and were necessary for expression of DTH. However, CD8 cell depletion did not abrogate DTH in mice immunized with either soluble cryptococcal Ag in complete Freund's adjuvant, or sheep red blood cells, which are mediated by CD4 cells. These data suggest that CD8 cells play a critical role in the cell-mediated immune response to C. neoformans. Based on this information, it may be possible to protect hosts with deficiencies of CD4 cells, such as in AIDS, by designing immunizing strategies for stimulating CD8 cells.

Animals↗
PubMed1994

Effect of granulocyte-macrophage colony-stimulating factor on rat alveolar macrophage anticryptococcal activity in vitro.

Cryptococcus neoformans, a pathogenic fungus usually acquired by inhalation, causes the most common lethal mycosis in AIDS. The resident lung phagocytes, alveolar macrophages (AM phi), inhibit growth of C. neoformans poorly unless activated by cytokines such as IFN-gamma. In this study, we examined the effect of rat AM phi of the potent hematopoietic and M phi-activating cytokine, granulocyte-macrophage CSF (GM-CSF), alone and in combination with other cytokines. Rat AM phi monolayers were preincubated with 0.1 to 1000 U/ml GM-CSF without or with other recombinant cytokines, and then were incubated with viable C. neoformans (strain H99/C3D). Growth inhibition was assessed by counting cryptococcal CFU at 24 and 48 h of coculture; AM phi proliferation was assessed by measuring both uptake of [3H]TdR and AM phi numbers. AM phi preincubated with GM-CSF for 5 days (but not for shorter periods) inhibited growth of C. neoformans. Anticryptococcal activity required direct contact of AM phi with C. neoformans, but once induced by preincubation, did not require continued exposure to GM-CSF. Induction of anticryptococcal activity by GM-CSF was dose dependent (maximal induction at 250 U/ml), and was due to both increased ingestion and killing. GM-CSF induced AM phi proliferation, but anticryptococcal activity was not due totally to increases in AM phi numbers, indicating AM phi activation by GM-CSF. GM-CSF-induced AM phi proliferation was increased by IL-6, unchanged by IL-8, and abolished by LPS or IFN-gamma. However, IL-6 did not increase GM-CSF-induced anticryptococal activity. The combination of GM-CSF and IFN-gamma showed rapid and sustained anticryptococcal activity, unlike either cytokine alone. Our in vitro data suggest that the combination of GM-CSF and IFN-gamma may have beneficial effects on host defense against C. neoformans in vivo.

Animals↗
PubMed1994

In vivo depletion of murine CD8 positive T cells impairs survival during infection with a highly virulent strain of Cryptococcus neoformans.

Cell-mediated immunity plays an important but incompletely understood role in host defense against Cryptococcus neoformans. Because of their multiple capacities as cytokine-secreting cells, cytotoxic cells, and antigen-specific suppressor cells, CD8 positive T lymphocytes could potentially either enhance or impair host defense against C. neoformans. To determine whether CD8 T cells enhance or inhibit host defence during an infection with a highly virulent strain of C. neoformans, we examined the effect of in vivo CD8 cell depletion on survival and on the number of organisms in mice infected by either the intratracheal or intravenous routes. Adequacy of depletion was confirmed both phenotypically and functionally. Regardless of the route of infection, we found that survival of mice depleted of CD8 T cells was significantly reduced compared to undepleted mice. Surprisingly, however, CD8 depletion did not alter organism burden measured by quantitative CFU assay in mice infected by either route. These data demonstrate that CD8 positive T cells participate in the immune response to a highly virulent strain of C. neoformans. By contrast to minimally virulent isolates that do not cause a life threatening infection, the immune response to a highly virulent isolate does not alter the burden of organisms, but does enhance host defense as it is necessary for the optimal survival of infected mice.

Animals↗