Mitogenic activity of bacterial lipopolysaccharides in vivo: morphological and functinal characterization of responding cells

Elevated internalization and cytotoxicity of polydispersed single-walled carbon nanotubes in activated B cells can be basis for preferential depletion of activated B cells in vivo

Uptake of polydispersed acid-functionalized single-walled carbon nanotubes (AF-SWCNTs) in resting and LPS-activated B cells was studied using fluorescence-tagged AF-SWCNTs (FAF-SWCNTs). Activated B cells internalized substantially higher amounts of FAF-SWCNTs [76.5% AF-SWCNT⁺ B cells, mean fluorescence intensity (MFI) 720.6] as compared to the resting B cells [39.5% AF-SWCNT⁺ B cells, MFI 198.5]. B cells in S and G2/M phases were found to have significantly higher uptake of FAF-SWCNTs as compared to cells in G0/G1 phase. Confocal microscopy indicated that AF-SWCNTs were essentially localized on cell membrane in resting B cells, whereas in activated B cells, AF-SWCNTs were distributed throughout the cytoplasm. Targeting of AF-SWCNTs specifically to activated B cells in vivo was examined by first administering intravenously LPS-activated B cells tagged with fluorescence tracer (CFSE) in mice, followed by FAF-SWCNTs through the same route. It was found that FAF-SWCNTs were specifically taken up by CFSE+CD19+-activated B cells (95% FAF-SWCNT⁺ B cells, MFI 3725) as compared to CFSE^- CD19⁺ resting B cells (31.1% FAF-SWCNT⁺ B cells, MFI 428). Administration (i.v.) of LPS resulted in a significant increase in the proportion of B cell in mouse spleen that was reduced by 68% by administering AF-SWCNTs. In control mice, the corresponding decrease in B cell proportion was 49%, which was significantly lower (p < 0.005) than the decline in LPS-treated mice. These results indicate that AF-SWCNTs may have the potential as an agent for depleting activated B cells in vivo.

Evaluation of T and B lymphocyte function in clinical practice using a flow cytometry based proliferation assay

The golden standard for functional evaluation of immunodeficiencies is the incorporation of [(3)H]-thymidine in a proliferation assay stimulated with mitogens. Recently developed whole blood proliferation assays have the advantage of parallel lymphocyte lineage analysis and in addition provide a non-radioactive alternative. Here we evaluate the Flow-cytometric Assay for Specific Cell-mediated Immune-response in Activated whole blood (FASCIA) in a comparison with [(3)H]-thymidine incorporation in four patients with severe combined immunodeficiency. The threshold for the minimum number of lymphocytes required for reliable responses in FASCIA is determined together with reference values from 100 healthy donors when stimulated with mitogens as well as antigen specific stimuli. Finally, responses against PWM and SEA+SEB stimuli are conducted with clinically relevant immunomodulatory compounds. We conclude that FASCIA is a rapid, stable and sensitive functional whole blood assay that requires small amounts of whole blood that can be used for reliable assessment of lymphocyte reactivity in patients.

Bone marrow immunosuppression in Salmonella-infected mice is prolonged following influenza virus infection

OBJECTIVE

It has been shown previously that infection with diverse viruses induces alterations in bone marrow lineage-specific progenitor cells. As complications arising from secondary bacterial infections can adversely affect the host, we investigated whether virally induced hematological alterations could contribute to the enhanced illness observed in such cases.

MATERIALS AND METHODS

Mice were infected with influenza virus alone or influenza virus followed by a vaccine strain of Salmonella typhimurium. The effects on hematopoiesis were analyzed by fluorescein-activated cell sorting analysis and immunohistology.

RESULTS

Systemic Salmonella typhimurium infection induces depletion of bone marrow erythroid and lymphoid cells. The depletion lasted longer in mice that had been previously infected with influenza virus, compared with mice that had been previously treated with allantoic fluid. Although an increase in splenic lymphoid cells was apparent in the spleens of Salmonella-infected mice, the majority of cells in the enlarged spleens were found to be both immature and mature erythrocytes.

CONCLUSION

These results show that bone marrow progenitor cell depletion induced by bacterial infection is prolonged following a viral infection. It is possible that hematological alterations may contribute to the enhanced clinical illness observed in consecutive viral:bacterial infections.

Lipopolysaccharide-induced hepatotoxicity is inhibited by the antioxidant melatonin

Oxidative damage to the liver of lipopolysaccharide-treated rats was evaluated using four parameters: level of lipid peroxidation, changes in total GSH and GSSG concentrations and hepatic morphology. Bacterial lipopolysaccharide (10 mg/kg b.w.) was injected i.p. either at 6, 16 or 24 h before animals were killed. Lipopolysaccharide increased lipid peroxidation most dramatically when it is injected 6 h before killing. Hepatic total GSH increased after lipopolysaccharide in a time-dependent manner. The highest level of GSSG and largest GSSG/total GSH ratio were also observed in the group of animals injected with lipopolysaccharide 6 h before tissue collection. In a second study, lipopolysaccharide was injected 6 h before the animals were killed, with or without 1 mg/kg b.w. melatonin. Melatonin totally abolished lipopolysaccharide-induced increase in lipid peroxidation, exaggerated the rise in total GSH and reversed the increase in GSSG concentration. The liver showed obvious histological degenerative changes after lipopolysaccharide, effects that were counteracted by melatonin administration. The protection conferred by melatonin is presumably due to its antioxidant activity.

Melatonin administration prevents lipopolysaccharide-induced oxidative damage in phenobarbital-treated animals

The protective effect of melatonin on lipopolysaccharide (LPS)-induced oxidative damage in phenobarbital-treated rats was measured using the following parameters: changes in total glutathione (tGSH) concentration, levels of oxidized glutathione (GSSG), the activity of the antioxidant enzyme glutathione peroxidase (GSH-PX) in both brain and liver, and the content of cytochrome P450 reductase in liver. Melatonin was injected intraperitoneally (ip, 4mg/kg BW) every hour for 4 h after LPS administration; control animals received 4 injections of diluent. LPS was given (ip, 4 mg/kg) 6 h before the animals were killed. Prior to the LPS injection, animals were pretreated with phenobarbital (PB), a stimulator of cytochrome P450 reductase, at a dose 80 mg/kg BW ip for 3 consecutive days. One group of animals received LPS together with Nw-nitro-L-arginine methyl ester (L-NAME), a blocker of nitric oxide synthase (NOS) (for 4 days given in drinking water at a concentration of 50 mM). In liver, PB, in all groups, increased significantly both the concentration of tGSH and the activity of GSH-PX. When the animals were injected with LPS the levels of tGSH and GSSG were significantly higher compared with other groups while melatonin and L-NAME significantly enhanced tGSH when compared with that in the LPS-treated rats. Melatonin alone reduced GSSG levels and enhanced the activity of GSH-PX in LPS-treated animals. Additionally, LPS diminished the content of cytochrome P450 reductase with this effect being largely prevented by L-NAME administration. Melatonin did not change the content of P450 either in PB- or LPS-treated animals.(ABSTRACT TRUNCATED AT 250 WORDS)

Evidence for lipid peroxidation in endotoxin-poisoned mice

Ethane has been identified and quantitated in air exhaled by mice following intraperitoneal injection of 20, 40, or 200 mg of Escherichia coli O111:B4 lipopolysaccharide (LPS) per kg. Significant increases in ethane concentration occurred within 1 to 5 h after LPS administration. In addition, increased concentrations of malondialdehyde were found in crude homogenates of livers obtained from mice 16 h after administration of 20 mg of LPS per kg. These results suggest that lipid peroxidation may be an important mechanism responsible for LPS toxicity.

A defined fragment of bacterial protein I (OmpF) is a polyclonal B-cell activator

Protein I from the outer membrane of Escherichia coli and other members of the family Enterobacteriaceae is a potent mitogen and polyclonal B-lymphocyte activator. To determine the part of the polypeptide responsible for biological activity, we cleaved the molecule into defined polypeptide fragments of approximate molecular weights 24,000, 15,000, 9,000, 7,000, and 3,000 by using the cyanogen bromide method. The fragments were purified by gel permeation chromatography and by preparative polyacrylamide gel electrophoresis. They were investigated for mitogenicity and for the induction of immunoglobulin synthesis in lymphocyte cultures from several inbred mouse strains. The fragment of molecular weight 24,000 turned out to be a potent polyclonal B-lymphocyte activator comparable to native protein I. The low-molecular-weight fragments exhibited only marginal effects. Neither purified T lymphocytes nor thymocytes were activated. Our results show that a defined fragment of protein I is responsible for its lymphocyte-stimulating activity.

Distribution of endotoxin and its effect on serum concentrations of C-reactive protein and cortisol in the plaice (Pleuronectes Platessa L.)

Bacterial endotoxins cause a significant increase in the serum concentration of both C-reactive protein (CRP) and cortisol in the plaice. The time course of the CRP elevation varies with the bacterial source, method of isolation of the endotoxin and the route of administration. Injection of the prostaglandin synthetase inhibitor, indomethacin, 2 hr before endotoxin, abolishes the increases in both CRP and cortisol, whereas it has no effect when given 6 hr after. Using [51Cr]labeled endotoxin, 40% of the total injected dose was localized in the kidney and 36% in the spleen, 24 hr after i.v. injection. Uptake was five times greater per g of spleen than of kidney.

Synthetic analogues of the N-terminal lipid part of bacterial lipoprotein are B-lymphocyte mitogens in vitro and in vivo

Two analogues of the N-terminal part of bacterial lipoprotein, S-[2,3-bis(palmitoyloxy)-(2RS)propyl]-N-palmitoyl-(R)-cysteine methyl ester ("tripalmitoyl cysteine") and S [-2,3-bis(palmitoyloxy)-(2RS)-propyl]-N-palmitoyl-(R)-cysteinyl-(S)-seryl-(S)-seryl-(S)-asparaginyl-(S)-alanine ("tripalmitoyl pentapeptide") were synthesized and tested for mitogenic activity. The compounds were potent mitogens towards mouse spleen cell cultures, as measured by 3H-thymidine incorporation and by hemolytic plaque assays. This activity was not dependent on the presence of serum. Tripalmitoyl pentapeptide had little, if any, effect on thymocytes. When injected intravenously into Balb/c mice, the synthetic compounds induced splenomegaly and polyclonal B-cell activation, the latter was evident from an increase in the number of plaque-forming cells against trinitrophenylated sheep red blood cells. Thus, a synthetic fragment of a bacterial surface component was shown to exhibit marked biological activity in vitro as well as in vivo.

Polyclonal activation of B-lymphocytes in vivo by Salmonella typhimurium lipoprotein

Lipoprotein prepared from the outer membrane of Salmonella typhimurium is a polyclonal activator of murine B-lymphocytes. It was shown to be mitogenic for splenic cultures, stimulating increased incorporation of [3H]thymidine into DNA. When injected intravenously into mice, the lipoprotein induced splenomegaly and polyclonal B-cell activation. The latter was evident from an increase in the number of plaque-forming cells against trinitrophenylated sheep erythrocytes. Similar results were obtained with Escherichia coli lipoprotein.

Hypertriglyceridemic very low density lipoproteins induce triglyceride synthesis and accumulation in mouse peritoneal macrophages

Triglyceride-rich lipoproteins may be responsible for the lipid accumulation in macrophages that can occur in hypertriglyceridemia. Chylomicrons and very low density lipoproteins (VLDL, total and with flotation constant [S(f)] 100-400) from fasting hypertriglyceridemic subjects induced a massive accumulation of oil red O-positive inclusions in unstimulated peritoneal macrophages. Cell viability was not affected. The predominant lipid that accumulated in cells exposed to hypertriglyceridemic VLDL was triglyceride. Hypertriglyceridemic VLDL stimulated the incorporation of [(14)C]oleate into cellular triglyceride up to ninefold in 16 h, but not into cholesteryl esters. Mass increase in cellular triglyceride was 38-fold. The stimulation of cellular triglyceride formation was dependent on time, temperature, and concentration of hypertriglyceridemic VLDL. By contrast, VLDL, low density, and high density lipoproteins from fasting normolipemic subjects had no significant effect on oleate incorporation into neutral lipids or on visible lipid accumulation.(125)I-Hypertriglyceridemic VLDL (S(f) 100-400) were degraded by macrophages in a dose-dependent manner, with 50 and 100% saturation observed at 3 and 24 mug protein/ml (2.5 and 20 nM), respectively. Hypertriglyceridemic VLDL inhibited the internalization and degradation of (125)I-hypertriglyceridemic VLDL (4 nM) by 50% at 3 nM. Cholesteryl ester-rich VLDL from cholesterol-fed rabbits gave 50% inhibition at 5 nM. Low density lipoproteins (LDL) inhibited by 10% at 5 nM and 40% at 47 nM. Acetyl LDL at 130 nM had no effect. We conclude that the massive triglyceride accumulation produced in macrophages by hypertriglyceridemic VLDL is a direct consequence of uptake via specific receptors that also recognize cholesteryl ester-rich VLDL and LDL but are distinct from the acetyl LDL receptor. Uptake of these triglyceride-rich lipoproteins by monocyte-macrophages in vivo may play a significant role in the pathophysiology of atherosclerosis.

Biological and immunological properties of Coxiella burnetii vaccines in C57BL/10ScN endotoxin-nonresponder mice

Vaccines prepared from Formalin-killed whole cells of Coxiella burnetii (Ohio strain) or from chloroform-methanol residue (CMR) and extract (CME) of such cells were examined for biological and immunological properties in male C57BL/10ScN endotoxin nonresponder mice. Vaccines containing killed whole cells induced a high incidence of gross pathology, as evidenced by liver necrosis, significant splenomegaly, and significant hepatomegaly in mice. The degree and onset of these pathological changes were directly and inversely proportional, respectively, to the dosage of killed organisms administered. Conversely, no splenomegaly, hepatomegaly, or liver necrosis were observed in mice inoculated with CMR or CME. Moreover, killed whole cells were lethal for mice at dosages of 150 to 1,200 micrograms, whereas no deaths were seen in animals given 1,200 micrograms of CMR. In addition, antibodies against phase I and phase II antigens of C. burnetii were detected in the sera of mice inoculated with either whole cells or CMR. Enhanced blastogenic response of splenic lymphocytes was observed when animals were vaccinated with killed whole cells and CMR but not with CME. Moreover, 80 to 90% of mice inoculated with 300 micrograms of the CMR were protected against a lethal challenge of viable rickettsiae, whereas only 50% of the animals given 300 micrograms of killed whole cells were protected. Treatments with CME were essentially without value, since no antibodies were detectable and no significant protection was elicited. Collectively, these results show that, although killed whole cells induced immunity in C57BL/10ScN mice, they induced deleterious tissue reactions, whereas CMR, which also induced immunity, was essentially nondeleterious, based on the parameters employed. These observations suggest that the chloroform-methanol-extractable component(s) is implicated in the deleterious tissue reactions and that the phase I and II antigens may not be involved in the induction of the pathology observed in C57BL/10ScN mice.

Antibodies to Tamm-Horsfall protein associated with renal damage and urinary tract infections in adults

Forty-seven adults with urinary tract infection (UTI), 9 with recent acute pyelonephritis and 38 with previous renal infection, were investigated for the presence of autoantibodies to Tamm-Horsfall protein (THP). All patients except 6 had or had had vesicoureteric reflux (VUR). In patients with recent acute pyelonephritis, only IgA antibodies were significantly elevated. Among the patients with previous UTI, more than 6 months before the time of testing, a graded response was found for IgG and IgM specific antibodies, with the lowest value in those with renal damage and elevated serum creatinine and the highest in those with a normal X-ray. A negative correlation was found between IgG antibodies to THP and elevated serum creatinine (r = -0.76, P less than 0.02). No significant correlation was found between VUR itself and antibodies to THP. A low IgG antibody level to THP in patients with a history of previous UTI seems to be a useful indicator of renal scarring. Possible immunologic mechanisms behind the low antibody level and the renal damage are discussed.

A kinetic study of glucocorticoid-heparin interaction on the in vivo DNA-synthesis of mouse lymphatic organs

The effect of glucocorticoids and heparin (in depot form) on the DNA-synthesis of thymus and spleen of mice was investigated by measuring (3H)dThd incorporation in a four day period. The kinetics of glucocorticoid action was similar whether the hormones were applied in 11 beta-hydroxy-, or keto-form and was characterized by a suppressive effect with a maximum on the first two days after administration. The suppressive effect of glucocorticoids proved to be more marked in the thymus than in the spleen. Heparin per se did not change thymidine incorporation into the lymphoid organs, but injected 3 hours prior steroid administration inhibited the suppressive effect of cortisone, but not that of hydrocortisone. In addition, heparin even reversed the suppressing effect of cortisone on splenic (3H)dThd uptake. The effects of heparin on glucocorticoid action could be only observed when the steroid was applied intraperitoneally. This observation and other data discussed suggest the involvement of peritoneal cells (macrophages) in glucocorticoid-heparin interactions on DNA-synthesis of lymphoid organs.

Mouse footpad infection by Pseudomonas aeruginosa: evidence for delayed hypersensitivity to specific bacterial antigen

Mouse hind footpad inoculation with 1 x 10(7) viable Pseudomonas aeruginosa cells produces a long-lasting, self-limiting disease process characterized by a bacterial multiplication that parallels the swelling of the infected footpad. Regional popliteal and inguinal lymph nodes and spleen of infected animals show cellular modifications which are almost entirely due to lymphocyte proliferation, as indicated by sponteneous DNA synthesis experiments in vitro. Furthermore, mice which had been infected in their footpad either 20 or 27 days previously and challenged with P. aeruginosa antigens into the controlateral footpad show, 24 h later, a marked increase in regional popliteal lymph node weight, indicating the development of delayed hypersensitivity to Pseudomonas antigens.

Depression of the antibody response in Pseudomonas aeruginosa-injected mice

Heat-killed Pseudomonas aeruginosa inhibit antibody response in C57BL/6 mice. The depression of this response is dependent on the dose of bacteria injected, on the time interval between microorganism injection and antigen administration, and on the nature of the antigen used. Cell transfer experiments provide evidence that suppressor cells are not operative in this model. Furthermore, the results show that P. aeruginosa induces a marked dose-dependent proliferation of spleen cells in vivo, and the in vitro targets of this proliferative effect are B lymphocytes. It is suggested that whole, heat-killed P. aeruginosa in vivo also behave as cell mitogens on B lymphocytes which, when strongly stimulated to proliferate, temporarily lose their capacity to mount a normal antibody response.

Effects of BCG infection on the susceptibility of mouse macrophages to endotoxin

Mice infected intravenously with Mycobacterium bovis (BCG) are 100 to 1,000 times more sensitive to the lethal effects of bacterial lipopolysaccharides (LPS). Since BCG infection results in macrophage activation and LPS may cause pathophysiological effects through interaction with this cell type, it was of interest to determine whether macrophages from BCG-infected animals were more susceptible to the toxic effects of LPS in vitro. When LPS-susceptible, C57BL/6 mice were infected with BCG, a significant reduction in the 50% lethal dose of LPS was first observed after 7 days and persisted for several weeks. Macrophages from these animals had greatly increased susceptibility to LPS in vitro, which correlated with the development of acquired cellular resistance as determined by their ability to inhibit the growth of Listeria monocytogenes. In contrast, BCG infection of C3H/HeJ mice, a strain resistant to LPS, did not alter the 50% lethal dose of LPS for these animals or increase the sensitivity of their peritoneal macrophages to LPS in vitro. These results indicate that susceptibility of BCG-infected mice to the lethal effects of LPS parallels the susceptibility of their macrophages in vitro; release of vasoactive substances from LPS-susceptible activated macrophages in vivo may be, in part, responsible for lethality.

Morphological and cytochemical characterization of cells infiltrating mouse lungs after influenza infection

To initiate evaluation of the cell-mediated immunological response to influenza virus in a major site of disease, lung cells were obtained by transpleural lavage from lungs of uninfected mice and from those infected 3 or 6 days previously with 5 50% mouse infectious doses (MID(50)) of avirulent (P3) or virulent (P9) influenza A Hong Kong (H3N2) virus. The number of cells recovered by lavage was dependent on the dose, time after inoculation, and the type of virus used for inoculation. Although lavage pools were shown to contain peripheral blood leukocytes, this contamination was shown to be consistently less than 5% of the total leukocytes harvested. Among the ca. 0.75 x 10(6) lavage cells obtained from each uninfected mouse, about 90% were macrophages or lymphocytes in approximately equal proportion. T, B, and null (lyphocytes lacking theta or surface immunoglobulin markers) lymphocytes averaged 23, 9, and 7% of cells in these suspensions, respectively. After infection with either P3 or P9 virus, increased numbers of activated macrophages and lymphoblasts were observed. The major change during P3 infection was an increase in absolute numbers of null lymphocytes. In contrast, during P9 infection, T and B lymphocytes and macrophages progressively increased in absolute numbers while null cells decreased. These data suggest that cell-mediated immunological responses to influenza virus occur in the lung during infection, but that the responses to virulent and avirulent variants may differ both qualitatively and quantitatively.

Strain-dependent cytotoxic effects of endotoxin for mouse peritoneal macrophages

The cytotoxic effects of bacterial lipopolysaccharides (LPS) on mouse leukocytes have been examined in vivo and in vitro. Intraperitoneal injection of LPS into C57BL/6 mice greatly reduced the recovery of mononuclear cells; LPS was cytotoxic for macrophages, but had a mitogenic effect on lymphocytes. Similar effects of LPS on peritoneal leukocytes were observed in vitro. When monolayers of adherent peritoneal cells were studied in vitro, cytotoxicity was also observed, suggesting that the effect of LPS on macrophages is direct and does not require participation by lymphocytes. Entirely different results were obtained when peritoneal macrophages from LPS-resistant C3H/HeJ mice were studied. LPS failed to activate lymphocytes and was not cytotoxic for macrophages in vitro or in vivo. The effect of LPS on polymorphonuclear leukocytes appeared to be the same in all mouse stains studied. Lipid A was shown to be the most biologically active portion of the LPS molecule. Whereas polysaccharide-deficient endotoxins extracted from rough mutants of Salmonella typhimurium were cytotoxic for macrophages in vitro, polysaccharides that lacked esterified fatty acids did not exhibit this activity. Since LPS may mediate its effects through affinity for mammalian cell membranes, the cellular unresponsiveness of C3H/H3J mice to LPS may reflect an inability of cells from LPS-resistant strains to interact with LPS at the membrane level.

Lipopolysaccharide effects on sensitive and resistant variant Chinese hamster ovary cell lines

Chinese hamster ovary (CHO . K1 . PRO) cell growth was inhibited by addition of a gram-negative bacterial lipopolysaccharide (LPS) to the cell culture medium. Growth inhibition began after three or four days of incubation, was dose-dependent up to a maximum at an LPS concentration of 500 microgram/ml and was accompanied by cell shape changes and enhanced cytoplasmic vacuolization. Formation of bizarre CHO . K1 . PRO cell shapes and vacuole formation were most pronounced after seven days of incubation with LPS and could be observed by light and electron microscopy. An LPS-resistant cell population was obtained by intermittent in vitro exposure to high levels of LPS; these variant cells or clones derived from them failed to display growth inhibition in the presence of LPS. A clone from the LPS-resistant variant population showed altered cell properties compared to the parental cell line which included changes in cell morphology, adhesion, and endocytosis. Parental cells was markedly density-inhibited, whereas the cariant clone exhibited considerable growth after confluency. The LPS-resistant variant cells showed a more elongated morphology than the parental line. No significant differences were observed between rates of detachment of parental and variant cells when sparse cultures of either line were removed from tissue culture dishes by ethylenediaminetetracetate (EDTA). However, at confluency approximately 100% of the variant cells versus 35% of the parental cells were removed by EDTA in one hour. Measurements of 125I-ferritin uptake by parental and variant cells showed approximately twenty-fold and twofold increases, respectively, in uptake induced by LPS when compared to untreated control cultures.