High Dimensional Immune Profiling Reveals Different Response Patterns in Active and Latent Tuberculosis Following Stimulation With Mycobacterial Glycolipids.

Upon infection with Mycobacterium tuberculosis (Mtb) the host immune response might clear the bacteria, control its growth leading to latent tuberculosis (LTB), or fail to control its growth resulting in active TB (ATB). There is however no clear understanding of the features underlying a more or less effective response. Mtb glycolipids are abundant in the bacterial cell envelope and modulate the immune response to Mtb, but the patterns of response to glycolipids are still underexplored. To identify the CD45+ leukocyte activation landscape induced by Mtb glycolipids in peripheral blood of ATB and LTB, we performed a detailed assessment of the immune response of PBMCs to the Mtb glycolipids lipoarabinomannan (LAM) and its biosynthetic precursor phosphatidyl-inositol mannoside (PIM), and purified-protein derivate (PPD). At 24 h of stimulation, cell profiling and secretome analysis was done using mass cytometry and high-multiplex immunoassay. PIM induced a diverse cytokine response, mainly affecting antigen-presenting cells to produce both pro-inflammatory and anti-inflammatory cytokines, but not IFN-γ, contrasting with PPD that was a strong inducer of IFN-γ. The effect of PIM on the antigen-presenting cells was partly TLR2-dependent. Expansion of monocyte subsets in response to PIM or LAM was reduced primarily in LTB as compared to healthy controls, suggesting a hyporesponsive/tolerance pattern derived from Mtb infection.

Lipidic Nanoparticles Comprising Phosphatidylinositol Mitigate Immunogenicity and Improve Efficacy of Recombinant Human Acid Alpha-Glucosidase in a Murine Model of Pompe Disease.

Enzyme replacement therapy with recombinant human acid α-glucosidase (rhGAA) is complicated by the formation of anti-rhGAA antibodies, a short circulating half-life, instability in the plasma, and limited uptake into target tissue. Previously, we have demonstrated that phosphatidylinositol (PI) containing liposomes can reduce the immunogenicity and extend plasma survival of factor VIII (FVIII) in a mouse model of hemophilia A. In this article, we investigate the ability of PI liposomes to be used as a delivery vehicle to overcome the issues that complicate therapy with rhGAA. In a murine model of Pompe disease, administration of PI-rhGAA mitigated the immunogenicity of rhGAA, resulting in a significantly lower formation of anti-rhGAA antibodies. PI-rhGAA also showed minimal improvements to the pharmacokinetic parameters and efficacy measures compared to free rhGAA. Overall, these data suggest that PI-rhGAA may have the potential to be a useful therapeutic option for improving the treatment of Pompe disease.

Soy phosphatidylinositol containing nanoparticle prolongs hemostatic activity of B-domain deleted factor VIII in hemophilia A mice.

Factor VIII (FVIII) replacement therapy in hemophilia A (HA) is complicated by a short half-life and high incidence of inhibitory antibody response against the protein. Phosphatidylinositol (PI) containing lipidic nanoparticles have previously been shown to reduce the immunogenicity and prolong the half-life of full length FVIII. It has not been established whether this prolongation in half-life improves hemostatic efficacy and whether this approach could be extended to the B-domain deleted form of FVIII (BDD FVIII). In the current study, we evaluated the pharmacokinetics (PK), hemostatic efficacy, and immunogenicity of BDD FVIII associated with PI nanoparticles (PI-BDD FVIII) in HA mice. Comparative human PK was predicted using an "informed scaling" approach. PI-BDD FVIII showed an approximate 1.5-fold increase in terminal half-life compared with free BDD FVIII following i.v. bolus doses of 40 IU/kg. PI-BDD FVIII-treated animals retained hemostatic efficacy longer than the free FVIII-treated group in a tail vein transection model of hemostasis. PI association reduced the development of inhibitory and binding antibodies against BDD FVIII after a series of i.v. injections. The combined improvements in circulating half-life and hemostatic efficacy could significantly prolong the time above clinically established therapeutic thresholds of prophylactic FVIII replacement therapy in humans.

Dietary phosphatidylinositol protects C57BL/6 mice from concanavalin A-induced liver injury by modulating immune cell functions.

SCOPE: Several recent studies have demonstrated that phospholipids (PLs) supplementation can modulate the function of cultured-immune cells. Furthermore, dietary PLs have been shown to ameliorate inflammatory processes and immune responses in arthritic and diabetic murine models, respectively. Thus, the aim of this study was to examine the immune-modulating activities of dietary soybean PLs in mice, with particular emphasis on the immune cell functions. METHODS AND RESULTS: Mice were fed semisynthetic diets for 6 weeks, which contained either 7% soybean oil or 5% soybean oil plus 2% of either PL: phosphatidylcholine (PC), phosphatidylinositol (PI), or phosphatidylserine (PS). Production of concanavalin A (Con A)-induced proinflammatory cytokines was significantly decreased in the splenocytes isolated from mice fed PI compared to other lipids. Supplementation of the diet with PI, but not with the other lipids, significantly suppressed the proinflammatory cytokine serum levels and the development of Con A-induced liver damages. CONCLUSION: These observations suggest that dietary PI influenced immune functions, resulting in the prevention of pathogenesis and development of the liver injury in mice.

Phosphatidylinositol di-mannoside and derivates modulate the immune response to and efficacy of a tuberculosis protein vaccine against Mycobacterium bovis infection.

Mycobacterium bovis infects a wide range of hosts, including domestic livestock, wildlife, and humans. Development of an effective vaccine protecting against bovine tuberculosis would provide a cost-effective tuberculosis control strategy. The objective of this study was to investigate the ability of phosphatidylinositol di-mannoside (PIM(2)) and its derivatives to modulate cell-mediated immunity in vivo in a bovine tuberculosis mouse model in response to a relevant antigen, namely a fusion protein of mycobacterial proteins Ag85A and ESAT-6. The addition of synthetic PIM(2) to the vaccine resulted in a significant reduction in lung bacterial counts and a cytokine profile indicating a Th 1 type immune response. The addition of the other PIM(2) derivatives to the vaccine or the fusion protein alone did not result in reduced lung bacterial counts; moreover, the addition of PIM(2)ME appeared to negate the induction of an antigen-specific interferon-γ response and protection against tuberculosis. In conclusion, this study provides further evidence that PIMs can function as potent adjuvants for protein or sub-unit vaccines, but subtle structural differences among PIMs can markedly alter the type of immune response induced.

Anti-obesity effect of phosphatidylinositol on diet-induced obesity in mice.

The aim of this study is to investigate the biodistribution of phosphatidylinositol (PI) after oral administration and its anti-obesity effect. When a suspension of radiolabeled PI was orally administered to mice and the biodistribution was examined, PI radioactivity accumulated in the liver compared to myo-inositol radioactivity at 48 h or later after administration. Then, a PI suspension was orally administered to diet-induced obesity (DIO) mice every 4 days, and the anti-obesity effect of PI was examined. As a result, PI suppressed the body weight increase of DIO mice and significantly reduced the plasma levels of aspartate aminotransferase (AST) and cholesterol. Furthermore, PI regulated the expression of some genes in the liver involved in lipid synthesis and metabolism. The present study demonstrated that PI accumulated in the liver after oral administration and exerted its anti-obesity effect on DIO by regulating the expression of certain genes involved in lipid metabolism in the liver.

A synthetic analogue of phosphatidylinositol mannoside is an efficient adjuvant.

We recently described the synthesis of an ether linked analogue of phosphatidylinositol dimannoside (PIM(2)ME). In the current study, PIM(2)ME was found to significantly enhance the release of the key Th1 cytokine interleukin-12 (IL-12) by dendritic cells (DCs) of naive mice in vitro, but not interleukin-10 (IL-10). Based on this result, it was hypothesized that PIM(2)ME would be an effective adjuvant for cell-mediated immune responses. Injections of PIM(2)ME alone did not lead to weight loss and did not have toxic side effects, based on biomarkers of toxicity in serum,demonstrating that the compound induced no apparent adverse side effects. Mice were vaccinated with the core antigens of the hepatitis C virus by itself or with three different adjuvants, namely PIM(2)ME, a commercial preparation of monophosphoryl lipid A (MPL) or a preparation of aluminium hydroxide gel (alum). A control group of animals received the antigen only with no adjuvants. Immune responses to the Hepatitis C viral antigens were monitored by measuring antigen-specific production of interferon-gamma (IFN-gamma), the p40 subunit of interleukin-12 (IL-12) and interleukin-10 (IL-10) to assess cell-mediated immune responses. Vaccination of mice with Hepatitis C viral antigens with the adjuvant PIM(2)ME led to a significant increase in cell-mediated immune responses (IFN-gamma and IL-12). Injection of Hepatitis C viral antigens in alum led to no enhancement of the cell-mediated immune response. We conclude that PIM(2)ME is an efficacious adjuvant for enhancing cell-mediated immunity, and induces no observable adverse effects.

Rapamycin by itself and additively in combination with carboplatin inhibits the growth of ovarian cancer cells.

OBJECTIVE: The current standard treatment for ovarian carcinoma, consisting of surgery followed by chemotherapy with carboplatin and paclitaxel, is fraught with a high rate of recurrences. We hypothesized that targeted inhibition of specific signaling pathways in combination with conventional drugs may increase chemotherapeutic efficacy. METHODS: We analyzed the expression and activation profiles of various signaling pathways in nine established ovarian cancer cell lines (CAOV-3, ES2, PA-1, SKOV-3, NIHOVCAR3, OV90, TOV112D, A1847, A2780) and 24 freshly procured human ovarian tumors. The PI3 kinase pathway component Akt was frequently overexpressed and/or activated in tumor cells. The effect of several PI3K pathway inhibitors (rapamycin, LY294002, SH-6) and rapamycin in combination with carboplatin on various tumor cell growth characteristics was tested in cell lines and fresh tumor-derived transient monolayer and organ cultures. RESULTS: Rapamycin by itself and additively with carboplatin inhibited the growth and invasion, and increased the sensitivity to anoikis of most of the ovarian cancer cell lines and fresh tumors. The additive inhibitory effect may be due to enhanced apoptosis as demonstrated by Poly-ADP-Ribose Polymerase (PARP) cleavage and Annexin V staining in cells treated with both rapamycin and carboplatin. CONCLUSIONS: Rapamycin in combination with standard chemotherapeutic agents may improve the efficiency of ovarian cancer treatment.

Dietary phosphatidylinositol prevents the development of nonalcoholic fatty liver disease in Zucker (fa/fa) rats.

Recent studies have shown that dietary phospholipids, especially phosphatidylcholine and phosphatidylserine, have various beneficial biological effects. However, there are not enough data concerning the physiological function of dietary phosphatidylinositol (PI). The metabolic syndrome, a cluster of metabolic abnormalities such as dyslipidemia, diabetes mellitus, and hypertension, is a widespread and increasingly prevalent disease in industrialized countries. Nonalcoholic fatty liver disease (NAFLD) is often associated with features of the metabolic syndrome. NAFLD describes the spectrum of liver damage ranging from hepatic steatosis to steatohepatitis, liver fibrosis, and cirrhosis, and it is emerging as the most common liver disease worldwide. The present study examined whether dietary PI protects Zucker ( fa/ fa) rats from the metabolic syndrome. For 4 weeks, rats were fed semisynthetic diets containing either 7% soybean oil or 5% soybean oil plus 2% PI. Dietary PI markedly prevented the development of hepatomegaly and hepatic steatosis and lowered hepatic injury markers in serum. Additionally, hyperinsulinemia was relieved by the feeding of dietary PI in Zucker rats. These effects were attributable to an increase in serum adiponectin, enhancement of fatty acid beta-oxidation, and suppression of mRNA expression of inflammatory genes in the liver. This is the first report that dietary PI increases serum adiponectin level and prevents the development of NAFLD in a rat model of the metabolic syndrome.

Interferon-gamma independent formation of pulmonary granuloma in mice by injections with trehalose dimycolate (cord factor), lipoarabinomannan and phosphatidylinositol mannosides isolated from Mycobacterium tuberculosis.

The mechanisms by which pulmonary granuloma formation is caused by administration of mycobacterial glycolipids such as trehalose dimycolate (TDM), lipoarabinomannan (LAM) and phosphatidylinositol mannosides (PIM) were investigated. When peritoneal and alveolar macrophages were stimulated with TDM, LAM and PIM in vitro, TDM exhibited the strongest tumour necrosis factor (TNF)-inducing activity. Responsiveness of macrophages from mice defected Toll-like receptor 4 (TLR4) was much higher than that of the wild-type mice. Although PIM and LAM also had a significant activity, LAM rather than PIM stimulated higher TNF-alpha production by alveolar macrophage. When mycobacterial glycolipids were injected as water-in-oil-in-water emulsion into mice via the tail vein, development of pulmonary granuloma in response to glycolipids were related closely to their TNF-inducing activity and TDM exhibited the strongest activity. Granuloma formation was observed not only in mice lacking interleukin (IL)-12 signalling but also interferon (IFN)-gamma knock-out mice. Granuloma formation caused by glycolipids correlated with TNF-alpha levels in lungs. Administration of anti-TNF-alpha monoclonal antibody into TDM-injected IFN-gamma knock-out mice decreased in granuloma formation, suggesting that development of pulmonary granuloma by mycobacterial glycolipids such as TDM is due to IFN-gamma-independent and TNF-alpha-dependent pathway.

Activation of dendritic cells by liposomes prepared from phosphatidylinositol mannosides from Mycobacterium bovis bacillus Calmette-Guerin and adjuvant activity in vivo.

Liposome vesicles could be formed at 65 degrees C from the chloroform-soluble, total polar lipids (TPL) extracted from Mycobacterium bovis bacillus Calmette-Guérin (BCG). Mice immunized with ovalbumin (OVA) entrapped in TPL liposomes produced both anti-OVA antibody and cytotoxic T lymphocyte responses. Murine bone marrow-derived dendritic cells were activated to secrete interleukin-6 (IL-6), IL-12, and tumor necrosis factor upon exposure to antigen-free TPL liposomes. Three phosphoglycolipids and three phospholipids comprising 96% of TPL were identified as phosphatidylinositol dimannoside, palmitoyl-phosphatidylinositol dimannoside, dipalmitoyl-phosphatidylinositol dimannoside, phosphatidylinositol, phosphatidylethanolamine, and cardiolipin. The activation of dendritic cells by liposomes prepared from each purified lipid component of TPL was evaluated in vitro. A basal activity of phosphatidylinositol liposomes to activate proinflammatory cytokine production appeared to be attributable to the tuberculosteric fatty acyl 19:0 chain characteristic of mycobacterial glycerolipids, as similar lipids lacking tuberculosteric chains showed little activity. Phosphatidylinositol dimannoside was identified as the primary lipid that activated dendritic cells to produce amounts of proinflammatory cytokines several times higher than the basal level, indicating the importance of mannose residues. Although the activity of phosphatidylinositol dimannoside was little influenced by palmitoylation of mannose at C-6, a further palmitoylation at inositol C-3 diminished the induction levels of IL-6 and IL-12. Further, OVA entrapped in palmitoyl-phosphatidylinositol dimannoside liposomes was delivered to dendritic cells for major histocompatibility complex class I presentation more effectively than TPL OVA-liposomes. BCG liposomes containing mannose lipids caused up-regulation of costimulatory molecules and CD40. Thus, the inclusion of pure phosphatidylinositol mannosides of BCG in lipid vesicle vaccines represents a simple and efficient option for targeting antigen delivery and providing immune stimulation.

Effect of dietary phospholipid level and phospholipid:neutral lipid value on the development of sea bass (Dicentrarchus labrax) larvae fed a compound diet.

The aim of the study was to determine the influence of dietary phospholipid concentration on survival and development in sea bass (Dicentrarchus labrax) larvae. Larvae were fed from day 9 to day 40 post-hatch with an isoproteic and isolipidic formulated diet with graded phospholipid levels from 27 to 116 g/kg DM and different phospholipid:neutral lipid values. The best growth (32 mg at the end of the experiment) survival (73 %) and larval quality (only 2 % of malformed larvae) were obtained in the larvae fed the diet containing 116 g phospholipid/kg DM (P<0.05). These results were related to the amount of phosphatidylcholine and phosphatidylinositol included in this diet (35 and 16 g/kg respectively). Amylase, alkaline phosphatase and aminopeptidase N activities revealed a proper maturation of the digestive tract in the two groups fed the highest phospholipid levels. Regulation of lipase and phospholipase A2 by the relative amount of their substrate in the diet occurred mainly at the transcriptional level. The response of pancreatic lipase to dietary neutral lipid was not linear. As in mammals 200 g triacylglycerol/kg diet seems to represent a threshold level above which the response of pancreatic lipase is maximal. The response of phospholipase A2 to dietary phospholipid content was gradual and showed a great modulation range in expression. Sea bass larvae have more efficient capacity to utilize dietary phospholipid than neutral lipids. For the first time a compound diet sustaining good growth, survival and skeletal development has been formulated and can be used in total replacement of live prey in the feeding sequence of marine fish larvae.

Intracellular delivery of phosphoinositides and inositol phosphates using polyamine carriers.

Phosphoinositide signaling regulates events in endocytosis and exocytosis, vesicular trafficking of proteins, transduction of extracellular signals, remodeling of the actin cytoskeleton, regulation of calcium flux, and apoptosis. Obtaining mechanistic insights in living cells is impeded by the membrane impermeability of these anionic lipids. We describe a carrier system for intracellular delivery of phosphoinositide polyphosphates (PIP(n)s) and fluorescently labeled PIP(n)s into living cells, such that intracellular localization can be directly observed. Preincubation of PIP(n)s or inositol phosphates with carrier polyamines produced complexes that entered mammalian, plant, yeast, bacterial, and protozoal cells in seconds to minutes via a nonendocytic mechanism. Time-dependent transit of both PIP(n)s and the carrier to specific cytosolic and nuclear compartments was readily visualized by fluorescence microscopy. Platelet-derived growth factor treatment of NIH 3T3 fibroblasts containing carrier-delivered phosphatidylinositol 4,5-bisphosphate [PtdIns(4, 5)P(2)]-7-nitrobenz-2-oxa-1,3-diazole resulted in the redistribution of the fluorescent signal, suggesting that fluorescent PtdIns(4, 5)P(2) was a substrate for phospholipase C. We also observed a calcium flux in NIH 3T3 cells when complexes of carrier and PtdIns(4, 5)P(2) or inositol 1,4,5-trisphosphate were added extracellularly. This simple intracellular delivery system allows for the efficient translocation of biologically active PIP(n)s, inositol phosphates, and their fluorescent derivatives into living cells in a physiologically relevant context.

Phosphatidylinositolmannoside-based liposomes induce no synthase in primed mouse peritoneal macrophages.

Liposomes prepared from phosphatidylinositolmannosides (extracted from BCG) and cholesterol are efficiently endocytosed by macrophages. Phagocytosis of particles or microbes modifies macrophage metabolism and in some cases, delivers potent stimulating signals to macrophages. We examined the effect of phosphatidylinositolmannoside-based liposomes on three macrophage functions especially important for host defenses: nitric oxide production, oxidative burst and TNF-alpha secretion. Phosphatidylinositolmannoside-based liposomes, added as empty vesicles, induced a strong NO synthase activity in mouse peritoneal macrophages primed either by interferon-gamma or by trehalose dimycolate. They also induced a moderate production of TNF-alpha. Phosphatidylinositolmannosides conferred activating properties to pH-sensitive liposomes. In contrast, liposomes composed of phosphatidylcholine and phosphatidylserine were unable to activate primed macrophages.

Phospholipids prevent enteric bacterial translocation in the early stage of experimental acute liver failure in the rat.

BACKGROUND: Bacterial infections and bacteremia in acute liver failure may at least partly be attributed to translocation of enteric bacteria. Attempts to prevent or treat such infections by the use of antibiotics may instead result in overgrowth of surviving microbes. METHODS: In the present study, normal saline (1.5 ml/100 g body weight), phosphatidylcholine (1.5 ml/100 g body weight), and phosphatidylinositol (1.5 ml/100 g body weight) were orally administered by means of a gastric tube both 12 h and 30 min before operation. Effects of enteric administration of phospholipids on the prevention of enteric bacterial translocation, intestinal and mucosal mass, and enterocyte protein contents in acute liver failure induced by subtotal liver resection in the rat were evaluated. RESULTS: The incidence of bacterial translocation increased significantly 2 and 4 h after 90% hepatectomy as compared with sham-operated animals. Enteric administration of phospholipids, however, significantly reduced the incidence of bacterial translocation after 90% hepatectomy. Phospholipid treatment prevented the postoperative decrease in intestinal mucosal mass and enterocyte protein content. CONCLUSIONS: Enteral administration of phospholipids thus seems to protect against translocation of enteric bacteria and prevent against a decrease in intestinal mucosal mass and enterocyte protein content after subtotal hepatectomy in the rat.

Role of topical phospholipids in the prophylaxis of silicone elastomer-associated infection in the abdominal cavity.

The present study evaluated the influence of phospholipids (phosphatidyl choline and phosphatidyl inositol) on the prevention of abdominal biomaterial-associated infection. Phospholipid-impregnated silicone elastomer (SE) fragments were either intraperitoneally implanted in rats or immersed in serum for 0, 4, and 14 days, and 3 x 10(9) cfu of 3H-labeled, live Escherichia coli were added in the peritoneal cavity or in vitro incubation medium. Three hours after incubation, the adherence of bacteria significantly decreased to phospholipid-impregnated SE fragments, which had been immersed/implanted for 0 and 4 days. However, the number of adhering bacteria did not differ between the impregnated and unimpregnated SE fragments after 14 days of immersion/implantation. A significantly lower number of adhering bacteria was noted on all unimpregnated SE fragments when phospholipid was supplemented in the peritoneal cavity or in vivo medium, compared with fragments with no supplement. The rate of bacterial DNA synthesis decreased significantly after incubation with phospholipid 2 h or more. Phospholipids did not further influence peritoneal morphology. Thus topical administration of phospholipids by impregnation to the surface of SE fragments or supplement in the incubation medium prevented bacterial adherence onto the SE fragments. This implies that the use of phospholipids might be a mode of preventing biomaterial-associated infections.

Orally administered phospholipids inhibit abdominal rubber-drain-induced bacterial translocation in the rat.

In order to determine the influence of phospholipid on abdominal biomaterial-induced bacterial translocation (BT), phsophatidylcholine (PC) or phosphatidylinositol (PI) was administered orally or intraperitoneally in rats with intraperitoneal implantation of 7-cm2 rubber drain pieces. Two days after surgery, the incidence of translocation to mesenteric lymph nodes and liver significantly decreased, the adherence of 3H-labeled Escherichia coli to the ileal mucosa was significantly inhibited and the phagocytic and bactericidal capacity of peritoneal macrophages increased in animals with PC or PI administered orally, but not intraperitoneally, as compared with rats without phospholipid administration. Scanning electron microscopy revealed a coating layer on the surface of the intestinal mucosa in phospholipid-gavaged rats. Thus, the results in the present study imply that oral, but not intraperitoneal, PC of PI administration reduces enteric BT induced by intraperitoneal drain implantation.

Liposomes as a carrier for mannophosphoinositide antigens of mycobacteria.

Phosphatidylcholine liposomes have been used as carriers of mannophosphoinositides (PIMs) of mycobacteria to examine their immunological properties. PIMs incorporated in egg phosphatidylcholine (EPC) liposomes elicited both humoral and cell-mediated immune responses in mice. Addition of cholesterol at 43 mole% to PC enhanced the immune responses while the reverse was observed with EPC liposomes bearing negative or positive charge. Liposomes made of dioleoylphosphatidylcholine (DOPC) with cholesterol (43 mole%) proved to be a better immunoadjuvant with this antigen as compared to those made of EPC or dipalmitoylphosphatidylcholine (DPPC). Our results suggest that DOPC liposomes containing cholesterol are better carriers for PIMs-antigen as compared to Freund's incomplete adjuvant.

Decreased serum level of tumor necrosis factor in animals treated with lipopolysaccharide and liposomes containing phosphatidylserine.

The rise in serum level of tumor necrosis factor (TNF), produced by lipopolysaccharide, has been measured in mice and rabbits treated with phospholipid liposomes. After 3 daily ip injection (mice) or 5 daily i.v. injections (rabbits) of 30 mg/kg of a phospholipid mixture enriched in phosphatidylserine, the action of lipopolysaccharide was 80-90% reduced. The phospholipid effect is dose dependent, requires a minimum of two daily injections before the administration of lipopolysaccharide, and is still manifest 2 days after the last phospholipid dose. Among individual purified phospholipids, phosphatidylserine and phosphatidylethanolamine were effective whereas phosphatidylinositol, phosphatidylglycerol, and phosphatidylcholine did not show significant activity. The data indicate that the parenteral administration of liposomes containing the aminophospholipids phosphatidylserine, and phosphatidylethanolamine is an efficient mode to reduce the endotoxin-induced production of TNF. As suggested by liposome pharmacokinetics, this effect may be related to phospholipid accumulation in the mononuclear phagocyte system of liver and spleen.