Surfactant protein A,but not surfactant protein D,is an opsonin for influenza A virus phagocytosis by rat alveolar macrophages

Surfactant protein A (SP-A) and surfactant protein D (SP-D) are collectins, and both proteins were shown to interact with influenza A virus and alveolar macrophages. However, it is not known whether SP-A and SP-D can serve as opsonins for the phagocytosis of influenza A virus by alveolar macrophages. In the present study, we investigated the opsonic activities of SP-A and SP-D for phagocytosis of fluorescein isothiocyanate (FITC)-labeled influenza A (H3N2) virus by rat alveolar macrophages using flow cytometry. SP-A enhanced the association of the virus with macrophages in a dose-dependent manner, reaching a maximum at an SP-A concentration of 60 μg/ml. An approximate threefold increase in association of influenza A virus with alveolar macrophages in the presence of SP-A over control incubations which contained no SP-A was observed. Half of the total cell-associated fluorescence could be quenched as demonstrated using the extracellular quenching dye trypan blue. These results indicate that SP-A mediates internalization of FITC-labeled influenza A (H3N2) virus by alveolar macrophages. Removal of the carbohydrate moiety of SP-A by N-glycosidase F treatment or cleavage of its sialic acid residues by neuraminidase abolished the enhancement of the phagocytosis of FITC-labeled influenza A virus by alveolar macrophages. Mannan, a mannose homopolysaccharide known to bind to the carbohydrate-binding domain of SP-A, did not affect the SP-A-mediated phagocytosis of FITC-labeled influenza by alveolar macrophages. In contrast, SP-D neither enhanced the association of FITC-labeled influenza A virus with alveolar macrophages nor affected the opsonic activity of SP-A for FITC-labeled influenza A (H3N2) virus at the SP-D concentrations tested. It is concluded that SP-A acts via its sialic acid residues as an opsonin in the phagocytosis of influenza A virus by alveolar macrophages.     

Amniotic fluid ingestion enhances opioid-mediated but not nonopioid-mediated analgesia

Ingestion of amniotic fluid or placenta by rats has been shown to enhance several types of opioid-mediated analgesia: that induced by morphine, footshock, vaginal/cervical stimulation, and late pregnancy. This enhancement has also been blocked by administration of opioid antagonists. The present study was designed to examine further the specificity of the enhancement effect for opioid-mediated analgesia by testing for enhancement following administration of aspirin, a nonopioid analgesic. The formalin test was used as the pain threshold assay. Amniotic fluid or beef bouillon was administered by orogastric tube to rats that were treated either with morphine sulfate or saline, or pretreated with naltrexone, then treated with aspirin or vehicle. Both morphine and aspirin treatments produced analgesia. Amniotic fluid significantly enhanced the analgesia produced by morphine, but did not enhance the analgesia produced by aspirin, further suggesting that the enhancing effect of amniotic fluid ingestion is specific for opioid-mediated analgesia, such as that existing at the start of parturition.     

Extracellular ATP is cytotoxic to mononuclear phagocytes but does not induce killing of intracellular Mycobacterium avium subsp. paratuberculosis

Mycobacterium avium subsp. paratuberculosis is the etiologic agent of Johne's disease, a chronic granulomatous enteritis in ruminants. ATP has been reported to induce cell death of macrophages and killing of Mycobacterium species in human and murine macrophages. In this study we investigated the short-term effect of ATP on the viability of M. avium subsp. paratuberculosis-infected bovine mononuclear phagocytes and the bacilli within them. Addition of 5 mM ATP to M. avium subsp. paratuberculosis-infected bovine monocytes resulted in 50% cytotoxicity of bovine monocytes at 24 h. Addition of 2'(3')-O-(4-benzoylbenzoyl) ATP triethylammonium salt (Bz-ATP), which is a longer-lived ATP homologue and purinergic receptor agonist, significantly increased the uptake of YO-PRO, which is a marker for membrane pore activation by P2X receptors. Addition of Bz-ATP also stimulated lactate dehydrogenase release and caspase-3 activity in infected bovine monocytes. Neither ATP nor Bz-ATP reduced the survival of M. avium subsp. paratuberculosis in bovine mononuclear phagocytes. Likewise, addition of ATP or Bz-ATP was cytotoxic to murine macrophage cell lines (RAW 264.7 and J774A.1 cells) but did not affect the intracellular survival of M. avium subsp. paratuberculosis, nor were the numbers of viable Mycobacterium avium subsp. avium or Mycobacterium bovis BCG cells altered in bovine mononuclear phagocytes or J774A.1 cells following ATP or Bz-ATP treatment. These data suggest that extracellular ATP does not induce the killing of intracellular M. avium subsp. paratuberculosis in bovine mononuclear phagocytes.     

CpG-ODN enhances ingestion of apoptotic neutrophils by macrophages

The clearance of apoptotic neutrophils by macrophages plays an important role in the process of inflammatory response. In the present study, we examined the ability of macrophages to ingest apoptotic neutrophils after activated by synthetic oligodeoxynucleotides containing CpG motifs (CpG-ODN) in vitro. The results showed that, while CpG-ODN at the experimental concentration had no cytotoxic effect on the viability of macrophages, the percentage of macrophages with ingested apoptotic neutrophils was increased from 23.6 to 42.30% by CpG-ODN stimulation. This effect was silenced when macrophages were treated with the mutation of CpG-ODN motifs. Both the total and cell surface protein of Toll-like receptor 9 (TLR9) expression in macrophages was up-regulated after CpG-ODN stimulation. While chloroquine (CHQ) had no effect on TLR9 expression in macrophages, it abolished the enhanced uptake of apoptotic neutrophils by macrophages. Although CpG-ODN had no significant effect on the IL-6 production, it was able to induce the increase of TNF-α protein expression and this effect was inhibited by CHQ pretreatment. Increased TNF-α production from macrophages induced by CpG-ODN stimulation was down-regulated after phagocytosis of apoptotic neutrophils. In conclusion, CpG-ODN could enhance the ingestion of apoptotic neutrophils by macrophages via TLR9 accompanied with an increasing in the level of TNF-α. After phagocytosis of apoptotic neutrophils, the increased TNF-α production from macrophages induced by CpG-ODN stimulation was down-regulated which the implications in the immune response remains for the further study.     

Phagocytosis and killing of Mycobacterium avium complex by human neutrophils

Organisms belonging to the Mycobacterium avium complex (MAC) cause life-threatening bacteremia in immunocompromised patients. Monocytes and macrophages are thought to be responsible for ingestion and killing of MAC. However, it has been suggested that neutrophils may play a role in the early immune response to MAC infection. Here, neutrophils in autologous plasma were incubated (at 0 and 37 degrees C) with M. avium labeled with Auramine O, a potent fluorochrome. Neutrophil phagocytosis was measured by flow cytometry. Neutrophils incubated at 37 degrees C showed an increase in fluorescence over time with a maximum at 15 min, whereas neutrophils on ice showed no time-dependent increase in FL1. At 15 min Fl 1 at 37 degrees C was twice as high as FL1 at 0 degrees C. Examination under the fluorescent microscope showed multiple intracellular fluorescent mycobacteria. Results in nine independent experiments showed time-dependent decrease of colony-forming units in neutrophil-associated live M. avium. Significant killing was observed within 30 min and was complete by 120 min. Observation by electron microscopy clearly confirmed the presence of intraphagosomal MAC, both intact and with evidence of degradation. These data demonstrate that MAC is rapidly phagocytized and killed by human neutrophils. The newly established flow cytometry method should be useful in further studies of neutrophil function and of the role of G-CSF and other cytokines in MAC disease.     

鸟结核分枝杆菌感染巨噬细胞后的外泌体刺激巨噬细胞产生的细胞因子及其蛋白质表达改变

目的 探讨鸟结核分枝杆菌(M.avium)感染巨噬细胞后分泌的外泌体[(+)外泌体]刺激巨噬细胞后产生的分子免疫机制及其差异蛋白质成分研究.方法 冷冻高速离心法收集经鸟分枝结核杆菌感染及未感染的巨噬细胞上清中的外泌体,然后利用外泌体刺激巨噬细胞;ELISA方法检测经外泌体刺激巨噬细胞后细胞上清中IFN-γ、TNF-α的含量;流式细胞术从蛋白水平检测巨噬细胞受外泌体刺激后CD80、CD86蛋白表达情况;2-DE MALDI-TOF/TOF MS技术分析鉴定巨噬细胞受M.avium感染后分泌的外泌体中的差异蛋白.结果 IFN-γ、TNF-α在(+)外泌体刺激巨噬细胞后培养上清中含量增加;CD80、CD86蛋白在巨噬细胞受(+)外泌体刺激后表达上调.外泌体经2-DE MALDI TOF/TOF MS分析获得18个差异蛋白,且质谱成功鉴定12个.结论 (+)外泌体促进巨噬细胞TNF-α、IFN-γ的分泌从而增强巨噬细胞的炎症反应,并且可促进巨噬细胞CD80、CD86蛋白表达增强;筛选出差异蛋白的功能与细胞骨架结构、蛋白质合成与加工,炎症反应密切相关.     

Surfactant protein A differentially regulates IFN-gamma- and LPS-induced nitrite production by rat alveolar macrophages

Although several studies have demonstrated that the pulmonary collectins surfactant protein (SP)-A and SP-D contribute to innate immunity by enhancing pathogen phagocytosis, the role of SP-A and SP-D in regulating production of free radicals and cytokines is controversial. We hypothesized that the state and mechanism of activation of the immune cell influence its response to SP-A. The effects of SP-A and SP-D on production of nitric oxide (NO) and inducible nitric oxide synthase (iNOS) were assessed in isolated rat alveolar macrophages activated with lipopolysaccharide (LPS), interferon gamma (IFN-gamma), or both agonists. SP-A inhibited production of NO and iNOS in macrophages stimulated with smooth LPS, which did not significantly bind SP-A, or rough LPS, which avidly bound SP-A. In contrast, SP-A enhanced production of NO and iNOS in cells stimulated with IFN-gamma or INF-gamma plus LPS. Neither SP-A nor SP-D affected baseline NO production, and SP-D did not significantly affect production of NO in cells stimulated with either LPS or IFN-gamma. These results suggest that SP-A contributes to the lung inflammatory response by exerting differential effects on the responses of immune cells, depending on their state and mechanism of activation.     

Differential responses of bovine macrophages to Mycobacterium avium subsp. paratuberculosis and Mycobacterium avium subsp. avium

Mycobacterium avium subsp. paratuberculosis and Mycobacterium avium subsp. avium are antigenically and genetically similar organisms; however, they differ in their virulence for cattle. M. avium subsp. paratuberculosis causes a chronic intestinal infection leading to a chronic wasting disease termed paratuberculosis or Johne's disease, whereas M. avium subsp. avium causes only a transient infection. We compared the response of bovine monocyte-derived macrophages to ingestion of M. avium subsp. paratuberculosis and M. avium subsp. avium organisms by determining organism survival, superoxide and nitric oxide production, and expression of the cytokines tumor necrosis factor alpha (TNF-alpha), gamma interferon (IFN-gamma), interleukin-8 (IL-8), IL-10, IL-12, and granulocyte-monocyte colony-stimulating factor (GM-CSF). Unlike M. avium subsp. paratuberculosis, macrophages were able to kill approximately half of the M. avium subsp. avium organisms after 96 h of incubation. This difference in killing efficiency was not related to differences in nitric oxide or superoxide production. Compared to macrophages activated with IFN-gamma and lipopolysaccharide, macrophages incubated with M. avium subsp. paratuberculosis showed greater expression of IL-10 and GM-CSF (all time points) and IL-8 (72 h) and less expression of IL-12 (72 h), IFN-gamma (6 h), and TNF-alpha (6 h). When cytokine expression by macrophages incubated with M. avium subsp. paratuberculosis was compared to those of macrophages incubated with M. avium subsp. avium, M. avium subsp. paratuberculosis-infected cells showed greater expression of IL-10 (6 and 24 h) and less expression of TNF-alpha (6 h). Therefore, the combination of inherent resistance to intracellular degradation and suppression of macrophage activation through oversecretion of IL-10 may contribute to the virulence of M. avium subsp. paratuberculosis in cattle.     

Activation of macrophages and interference with CD4+ T-cell stimulation by Mycobacterium avium subspecies paratuberculosis and Mycobacterium avium subspecies avium

Mycobacterium avium subspecies paratuberculosis (M. ptb) and M. avium subspecies avium (M. avium) are closely related but exhibit significant differences in their interaction with the host immune system. The macrophage line, J774, was infected with M. ptb and M. avium and analysed for cytokine production and stimulatory capacity towards antigen-specific CD4+ T cells. Under all conditions J774 cells were activated to produce proinflammatory cytokines. No influence on the expression of major histocompatibility complex (MHC) class II, intracellular adhesion molecule-1 (ICAM-1), B7.1, B7.2 or CD40 was found. However, the antigen-specific stimulatory capacity of J774 cells for a CD4+ T-cell line was significantly inhibited after infection with M. ptb, but not with M. avium. When a T-cell hybridoma expressing a T-cell receptor identical to that of the T-cell line was used, this inhibition was not observed, suggesting that costimulation which is essential for the CD4+ T-cell line is influenced by the pathogenic bacterium M. ptb.     

Human immunodeficiency virus type 1 enhances intracellular growth of Mycobacterium avium in human macrophages.

Disseminated Mycobacterium avium infections are common in patients with AIDS and result in a reduced life expectancy. Human monocytes/macrophages are important target cells for both human immunodeficiency virus (HIV) and M. avium. We have studied the interaction in vitro of M. avium and HIV type 1 (HIV-1) in human macrophages. Human monocytes isolated from the peripheral blood of healthy individuals were infected with HIV-1, M. avium, or both. The intracellular growth of M. avium and the replication of HIV-1 were monitored for up to 5 weeks. Intracellular mycobacterial growth was seen in all M. avium infected cell cultures and was paralleled by increased production of interleukin 1 alpha and beta. Preinfection of the macrophages with HIV-1 reduced the interleukin 1 production and accelerated the intracellular growth of M. avium. These findings may explain in part the impaired control of mycobacterial infections seen with patients with AIDS.     

Oxidative and non-oxidative intracellular killing of Mycobacterium avium complex

Among mycobacteria, those belonging to the Mycobacterium avium complex (MAC) are the most common cause of bacteremia in AIDS patients. To understand better the mechanisms by which human macrophages kill intracellular MAC, we studied in an in vitro test system transparent morphotypes of the three most common bacteremic serotypes from AIDS patients and an opaque variant, obtained in vitro from the most mouse-virulent strain (MAC 101). The three serotypes differed in susceptibility to oxidative bactericidal mechanisms of macrophages. The transparent morphotype of strain 101 (serotype 1) was completely resistant to the intracellular killing effects of a phagocyte's reactive oxygen radicals and hydrogen peroxide, whereas strains 109 (serotype 4), 100 (serotype 8), and the opaque variant from strain 101 were killed by oxidative bactericidal mechanisms. However, even for these bacteria, non-oxidative mechanisms appear to have a role in intracellular killing.     

Surfactant protein D enhances phagocytosis and killing of unencapsulated phase variants of Klebsiella pneumoniae

Pulmonary surfactant protein D (SP-D) is a collagenous C-type lectin (collectin) that is secreted into the alveoli and distal airways of the lung. We have studied the interactions of SP-D and alveolar macrophages with Klebsiella pneumoniae, a common cause of nosocomial pneumonia. SP-D does not agglutinate encapsulated K. pneumoniae but selectively agglutinates spontaneous, unencapsulated phase variants, such as Klebsiella strain K50-3OF, through interactions with their lipopolysaccharides (LPS). These effects are calcium dependent and inhibited with maltose but not lactose, consistent with involvement of the SP-D carbohydrate recognition domain. Precoating of K50-3OF with SP-D enhances the phagocytosis and killing of these organisms by rat alveolar macrophages in cell culture and stimulates the production of nitric oxide by the NR-8383 rat alveolar macrophage cell line. SP-D similarly enhances the NO response to K50-3OF LPS adsorbed to Latex beads under conditions where soluble LPS or SP-D, or soluble complexes of SP-D and LPS, do not stimulate NO production. Our studies demonstrate that interactions of SP-D with exposed arrays of Klebsiella LPS on a particulate surface can enhance the host defense activities of alveolar macrophages and suggest that activation of macrophages by SP-D requires binding to microorganisms or other particulate ligands. Because unencapsulated phase variants are likely to be responsible for the initial stages of tissue invasion and infection, we speculate that SP-D-mediated agglutination and/or opsonization of K. pneumoniae is an important defense mechanism for this respiratory pathogen in otherwise healthy individuals.     

Apoptosis of human monocytes and macrophages by Mycobacterium avium sonicate.

Mycobacterium avium is an intracellular organism which multiplies predominantly within human macrophages. This organism has previously been shown to induce apoptosis in human macrophages. With a view to identifying M. avium components that induce cell death in infected host cells, sonicated extracts of M. avium as well as individual components isolated from the M. avium sonicate were tested in various assays with a human monocytic cell line (THP-1). THP-1 cells incubated with M. avium sonicate showed significantly reduced viability after a 2-day exposure compared to control cells incubated with media alone. This effect was dose dependent, with only 6.6% +/- 5.2% and 48.8% +/- 10.3% of the cells being viable by trypan blue exclusion at 600 and 300 microg/ml, respectively. Control cells, on the other hand, exhibited a viability of 98.8% +/- 1.0%. In addition, an 80% ammonium sulfate fraction of the M. avium sonicate and the previously characterized 68-kDa protein were found to have similar effects on THP-1 cells. In both cases, the reduction in viability was due to apoptosis characterized by chromatin condensation, DNA fragmentation by agarose gel electrophoresis, or terminal deoxynucleotidyl transferase-mediated d-UTP nick end labeling (TUNEL) and release of nuclear matrix protein (NMP) into the culture medium. M. avium sonicate-induced apoptosis of THP-1 cells was completely inhibited by the commonly used antioxidants pyrrolidinedithiocarbamate (PDTC) and butylated hydroxyanisole (BHA), indicating that the generation of free oxygen radicals may be responsible for inducing cell death. M. avium sonicate was found to induce apoptosis of monocyte-derived macrophages (MDMs) as well. This effect was not reversed in the presence of PDTC and was not accompanied with DNA fragmentation when determined by agarose gel electrophoresis, as seen in the case of THP-1 cells. However, these MDMs were found to contain fragmented DNA by TUNEL. These findings suggest that the mechanism of cell death in MDMs may be different from that observed with THP-1 cells. Furthermore, these results provide new insight into the effect of M. avium components on host cell responses during M. avium infection.     

Regulation of expression of major histocompatibility antigens by bovine macrophages infected with Mycobacterium avium subsp. paratuberculosis or Mycobacterium avium subsp. avium

Mycobacterium avium subsp. paratuberculosis and Mycobacterium avium subsp. avium are antigenically and genetically very similar organisms; however, they differ markedly in their virulence for cattle. We evaluated the capacity of bovine macrophages infected with M. avium subsp. paratuberculosis or M. avium subsp. avium to express major histocompatibility complex (MHC) class I and class II antigens on their surface and to interact with primed autologous lymphocytes. Our results indicate that infection of bovine macrophages with M. avium subsp. paratuberculosis promoted the downregulation of MHC class I and class II molecules on the macrophage surface within 24 and 12 h, respectively. Alternatively, MHC class II expression by M. avium subsp. avium-infected macrophages was not detected until 24 h after infection, and the magnitude of the decrease was smaller. Decreased MHC class I expression by M. avium subsp. avium-infected macrophages was not detected. Unlike M. avium subsp. paratuberculosis-infected macrophages, M. avium subsp. avium-infected macrophages upregulated MHC class I and class II expression after activation by gamma interferon or tumor necrosis factor alpha. Further, M. avium subsp. avium-infected macrophages were lysed by primed autologous lymphocytes, whereas M. avium subsp. paratuberculosis-infected macrophages were not. Overall, the results support the hypothesis that the difference in the virulence of M. avium subsp. paratuberculosis and M. avium subsp. avium for cattle is dependent on a difference in the capacity of the organisms to suppress mycobacterial antigen presentation to T lymphocytes.     

A pre-existing infection by Mycobacterium avium subsp. avium modulates anti-Cryptococcus neoformans and anti-Candida albicans activities in human macrophages

Mycobacterium avium is a facultative intracellular microorganism, able to survive and multiply within mammalian macrophages by circumventing antimicrobial mechanisms. In this study we hypothesize that pre-existing M. avium infection could result in macrophage superinfections by other microorganisms. We found that 24 h after ingestion of M. avium at a low multiplicity of infection, macrophages are unable to efficiently produce superoxide anions when over-stimulated with phorbol esters, and that the generation of oxidative burst is only partially restored 72 h after bacteria ingestion. We also demonstrate that intracellular killing of Cryptococcus neoformans is markedly impaired in human macrophages that have previously ingested M. avium (but not other bacteria such as Escherichia coli). This inhibitory effect is observed with live mycobacteria, but not when heat-inactivated bacteria are ingested. In contrast, when Candida albicans is given to macrophages instead of C. neoformans, an enhancement of intracellular killing is observed, suggesting that cytocidal mechanisms other than respiratory burst are involved in the anti- Candidacidal activity of macrophages.     

Exogenous myeloperoxidase enhances bacterial phagocytosis and intracellular killing by macrophages.

It is well documented that myeloperoxidase (MyPo) contributes to the bacterial activities of neutrophils and monocytes. Since mature macrophages (M phi) are devoid of this enzyme, its participation in M phi-mediated phagocytes and bacterial killing has not been completely defined. The present study demonstrates the exogenously added MyPo, at physiological levels, enhances both phagocytosis and killing of Escherichia coli. Murine peritoneal M phi were exposed to various concentrations of MyPo for different time intervals. Viable opsonized E. coli was added either prior to or after addition of MyPo. Thioglycolate-induced but not resident M pho exhibited an increase in the number of phagocytizing cells. Both resident and thioglycolate-induced M phi demonstrated increased bactericidal activity. Physiological levels of soluble MyPo also induced a significant increase in chemiluminescence. Since luminol-dependent chemiluminescence measures reactive oxygen intermediate production, studies were done to determine whether superoxide anion or H2O2 was involved in MyPo-induced M pho killing. Both superoxide dismutase and catalase ablated MyPo-induced bactericidal activity. The above data suggest that soluble MyPo, released from neutrophils at a site of infection or inflammation, can enhance both phagocytosis and killing of microorganisms.     

Pulmonary surfactant protein A enhances the host-defense mechanism of rat alveolar macrophages

The effects of surfactant, surfactant lipids, and surfactant protein A (SP-A) on the surface phagocytosis of [3H]thymidine-labeled Staphylococcus aureus (SAE) by rat alveolar macrophages were studied. Alveolar macrophages only ingest SAE when the bacteria are opsonized with rat serum prior to incubation with alveolar macrophages. Preincubation or "opsonization" of the bacteria with surfactant did not result in phagocytosis by the macrophages. However, preincubation of the macrophages with surfactant increased the phagocytosis of rat serum-opsonized bacteria by approximately 70% when compared to the control macrophages. The factor present in surfactant causing the stimulation of the phagocytosis is probably SP-A. Preincubation of macrophages with human SP-A enhanced the phagocytosis to the same extent as whole surfactant, whereas preincubation with surfactant lipids had no effect on the phagocytosis. The SP-A-induced enhancement of the phagocytosis is time, temperature, and concentration dependent. Phagocytosis of opsonized SAE by alveolar macrophages was maximal after 15 min of incubation and at an SP-A concentration of 1 micrograms/ml. No phagocytosis occurred at 0 degrees C. In addition, whole surfactant and SP-A induce a lucigenin-dependent chemiluminescence response in alveolar macrophages. The chemiluminescence response is initiated after 15 min of incubation and reaches a maximum after 30 min. The concentration of SP-A needed for an optimal response is in the same order of magnitude as the concentration needed for maximal enhancement of the phagocytosis of SAE by alveolar macrophages.(ABSTRACT TRUNCATED AT 250 WORDS)     

A PE protein expressed by Mycobacterium avium is an effective T-cell immunogen

Infection of mice with Mycobacterium avium or immunization with a novel PE gene expressed by M. avium (MaPE) showed that a dominant T-cell immune response was elicited. Immunization with an MaPE DNA vaccine protected mice against an aerosol challenge with Mycobacterium tuberculosis, suggesting that mycobacteria express PE antigens with cross-protective T-cell epitopes.     

Surfactant protein A binding to cytomegalovirus proteins enhances virus entry into rat lung cells

The role of surfactant protein (SP)-A in cytomegalovirus (CMV) infection of the lung was investigated. We found that SP-A binds to various immobilized human CMV proteins and those exposed on the surface of infected embryonal lung fibroblasts. The interaction between SP-A and immobilized CMV proteins was found to be calcium-dependent and inhibited by mannan, suggesting involvement of the carbohydrate recognition domain of SP-A and high-mannose carbohydrate residues of viral envelope glycoproteins. Using flow cytometry and confocal laser fluorescence microscopy in the rat model we showed that preincubation of rat CMV with SP-A stimulates its binding and internalization by rat type II pneumocytes and alveolar tissue macrophages. This effect was concentration- and Ca(2+)-dependent but was not inhibited by mannan. Therefore, the domains of SP-A involved in SP-A CMV interaction and in interaction of the SP-A/virus complex with rat lung cells are distinct. Additionally, in the human CMV model, sheep as well as human proteinosis SP-A did not significantly affect human CMV replication in embryonal lung fibroblasts. Thus, SP-A may contribute to CMV-associated pathology of the lung by increasing the efficiency of target cell infection.     

鸟结核分枝杆菌感染巨噬细胞的分子免疫机制研究

目的:探讨鸟结核分枝杆菌感染巨噬细胞后产生的免疫防御分子机制.方法:通过抗酸染色分析巨噬细胞受M.avium感染后吞噬M.aviu的能力;并运用real-time PCR及流式细胞术从基因和蛋白水平检测巨噬细胞受M.avium感染后细胞CD80、CD86的表达情况;同时以ELISA方法检测M.avium感染巨噬细胞后细胞上清中IFN-γ、TNF-α含量.结果:巨噬细胞随着时间变化吞噬M.avium的量不断增加;real-time PCR与流式细胞术结果表明巨噬细胞在受M.avium感染后CD80、CD86基因与蛋白表达上调.同时ELISA检测结果表明IFN-γ、TNF-α在M.avium感染巨噬细胞后培养上清中含量增加.结论:巨噬细胞吞噬M.avium的能力随时间变化而增强.M.avium可促进巨噬细胞表面信号分子CD80、CD86在基因及蛋白水平表达表达增强,并促进巨噬细胞TNF-α、IFN-γ的分泌从而增强巨噬细胞的炎症反应.