Granulocyte colony-stimulating factor (G-CSF) depresses angiogenesis in vivo and in vitro: implications for sourcing cells for vascular regeneration therapy

SUMMARY BACKGROUND

The most common source of hematopoietic progenitor cells (HPCs) for hematopoietic reconstitution comprises granulocyte colony-stimulating factor (G-CSF)-mobilized peripheral blood stem cells (PBSCs). It has been proposed that endothelial progenitor cells (EPCs) share precursors with HPCs, and that EPC release may accompany HPC mobilization to the circulation following G-CSF administration.

OBJECTIVE

To investigate EPC activity following HPC mobilization, and the direct effects of exogenous G-CSF administration on human umbilical vein endothelial cells (HUVECs) and endothelial outgrowth cells (EOCs), using in vitro and in vivo correlates of angiogenesis.

PATIENTS/METHODS

Heparinized venous blood samples were collected from healthy volunteers and from cord blood at parturition. G-CSF-mobilized samples were collected before administration, at apheresis harvest, and at follow-up. PBSCs were phenotyped by flow cytometry, and cultured in standard colony-forming unit (CFU)-EPC and EOC assays. The effect of exogenous G-CSF was investigated by addition of it to HUVECs and EOCs in standard tubule formation and aortic ring assays, and in an in vivo sponge implantation model.

RESULTS

Our data show that G-CSF mobilization of PBSCs produces a profound, reversible depression of circulating CFU-EPCs. Furthermore, G-CSF administration did not mobilize CD34+CD133- cells, which include precursors of EOCs. No EOCs were cultured from any mobilized PBSCs studied. Exogenous G-CSF inhibited CFU-EPC generation, HUVEC and EOC tubule formation, microvessel outgrowth, and implanted sponge vascularization in mice.

CONCLUSIONS

G-CSF administration depresses both endothelial cell angiogenesis and monocyte proangiogenic activity, and we suggest that any angiogenic benefit observed following implantation of cells mobilized by G-CSF may come only from a paracrine effect from HPCs.

Influence of menstrual cycle on circulating endothelial progenitor cells

BACKGROUND

Endothelial progenitor cells (EPCs) are circulating mononuclear cells that participate in angiogenesis. The aim of this study was to determine the influence of the menstrual cycle on the number and function of EPCs, and to investigate their relationship with circulating concentrations of sex steroids and inflammatory mediators.

METHODS

Ten healthy nulliparous, premenopausal, non-smoking women with regular menses were studied over a single menstrual cycle. Venepuncture was performed in the menstrual, follicular, peri-ovulatory and luteal phases. EPCs were quantified by flow cytometry (CD133(+)CD34(+)KDR(+) phenotype) and the colony-forming unit (CFU-EPC) functional assay. Circulating concentrations of estradiol, progesterone and inflammatory mediators (TNF-alpha, IL-6, sICAM-1 and VEGF) were measured by immunoassays.

RESULTS

The numbers of CD133(+)CD34(+)KDR(+) cells were higher in the follicular phase (0.99 +/- 0.3 x 10(6) cells/l) compared with the peri-ovulatory phase (0.29 +/- 0.1 x 10(6) cells/l; P < 0.05). In contrast, the numbers of CFU-EPCs did not vary over the menstrual cycle. There were no correlations between EPCs and concentrations of either circulating sex steroids or inflammatory mediators.

CONCLUSIONS

CD133(+)CD34(+)KDR(+) cells but not CFU-EPCs vary during the menstrual cycle. Our findings suggest a potential role for circulating EPCs in the normal cycle of physiological angiogenesis and repair of the uterine endometrium that is independent of circulating sex steroids or inflammatory mediators.

Endotoxin immunity and the development of the systemic inflammatory response syndrome in critically ill children

BACKGROUND

The systemic inflammatory response syndrome (SIRS) may be triggered by endotoxin. Humans have antibodies directed against the core of endotoxin (endotoxin core antibodies, EndoCAb) that appear to be protective following surgery and in sepsis. We hypothesised that children with elevated antibodies to endotoxin core would be less likely to develop SIRS in their initial period on intensive care. Because of the existing literature we defined two sub-groups according to the primary reason for ICU admission: infection and non-infection.

METHODS

We recruited 139 consecutive patients admitted to a paediatric intensive care unit (PICU) with more than one organ failure for longer than 12 h as part of another study. Patients were classified on admission to PICU as having an infectious or a non-infections diagnosis. The occurrence of SIRS within 48 h of admission was recorded along with detailed clinical and demographic data, EndoCAb concentration and the potential confounding variables C-reactive protein and mannose-binding lectin.

RESULTS

In the 71 patients admitted without infection (primarily post-operative and head injured) IgG EndoCAb was significantly lower in patients who developed SIRS than those who did not (72 vs. 131 MU/ml), independent of potential confounding variables. In patients with infection there was no significant difference in IgG EndoCAb between children developing SIRS and those who did not (111 vs. 80 MU/ml).

CONCLUSION

Head injured and post-operative patients admitted to PICU who develop early SIRS have significantly lower serum IgG EndoCAb levels than those who do not.

Intraoperative oesophageal Doppler guided fluid management shortens postoperative hospital stay after major bowel surgery

BACKGROUND

Occult hypovolaemia is a key factor in the aetiology of postoperative morbidity and may not be detected by routine heart rate and arterial pressure measurements. Intraoperative gut hypoperfusion during major surgery is associated with increased morbidity and postoperative hospital stay. We assessed whether using intraoperative oesophageal Doppler guided fluid management to minimize hypovolaemia would reduce postoperative hospital stay and the time before return of gut function after colorectal surgery.

METHODS

This single centre, blinded, prospective controlled trial randomized 128 consecutive consenting patients undergoing colorectal resection to oesophageal Doppler guided or central venous pressure (CVP)-based (conventional) intraoperative fluid management. The intervention group patients followed a dynamic oesophageal Doppler guided fluid protocol whereas control patients were managed using routine cardiovascular monitoring aiming for a CVP between 12 and 15 mm Hg.

RESULTS

The median postoperative stay in the Doppler guided fluid group was 10 vs 11.5 days in the control group P<0.05. The median time to resuming full diet in the Doppler guided fluid group was 6 vs 7 for controls P<0.001. Doppler patients achieved significantly higher cardiac output, stroke volume, and oxygen delivery. Twenty-nine (45.3%) control patients suffered gastrointestinal morbidity compared with nine (14.1%) in the Doppler guided fluid group P<0.001, overall morbidity was also significantly higher in the control group P=0.05.

CONCLUSIONS

Intraoperative oesophageal Doppler guided fluid management was associated with a 1.5-day median reduction in postoperative hospital stay. Patients recovered gut function significantly faster and suffered significantly less gastrointestinal and overall morbidity.

A descriptive study of the variation in baseline levels of antiendotoxin core antibodies between US and UK populations

Low levels of naturally occurring antibodies to the core section of endotoxin (EndoCAb) have been shown to be predictors of poor outcome following major surgery. We performed a retrospective study comparing pre-operative levels in US surgical patients, UK surgical patients and healthy volunteers. Both IgM and IgG EndoCAb levels were higher in the US surgical patients when compared with the other groups (approximately twice as high in the case of IgG EndoCAb). This may reflect genetic or environmental variability between the patient groups, differences in the disease processes, the disparity in the delivery of health care between the two countries or degradation of the samples in transfer.

Calcitonin precursors: early markers of gut barrier dysfunction in patients with acute pancreatitis

BACKGROUND

Severe acute pancreatitis is associated with an early increase in intestinal permeability and endotoxemia. Endotoxin is a potent stimulator for the production and release of procalcitonin and its components (calcitonin precursors; [CTpr]). The aim of this study is to evaluate the role of plasma CTpr as an early marker for gut barrier dysfunction in patients with acute pancreatitis.

METHODS

Intestinal permeability to macromolecules (polyethylene glycol 3350), serum endotoxin and antiendotoxin core antibodies, plasma CTpr, and serum C-reactive protein (CRP) were measured on admission in 60 patients with acute pancreatitis. Attacks were classified as mild (n = 48) or severe (n = 12) according to the Atlanta criteria.

RESULTS

Compared with mild attacks of acute pancreatitis, severe attacks were significantly associated with an increase in intestinal permeability index (median: 0.02 vs. 0.006, P < 0.001), the frequency of endotoxemia (73% vs. 41%, P = 0.04), and the extent of depletion of serum IgM antiendotoxin antibodies (median: 43 MMU vs. 100 MMU, P = 0.004). Plasma CTpr levels were significantly elevated in patients with severe attacks compared with mild attacks on both the day of admission and on day 3 (median: 64 vs. 22 fmol/mL, P = 0.03; and 90 vs. 29 fmol/mL, P = 0.003 respectively). A positive and significant correlation was observed between the admission serum endotoxin and plasma CTpr levels on admission (r = 0.7, P < 0.0001) and on day 3 (r = 0.96, P < 0.0001), and between plasma CTpr on day 7 and the intestinal permeability index (r = 0.85, P = 0.0001). In contrast, only a weak positive correlation was observed between peak serum levels of CRP and plasma CTpr on admission (r = 0.3, P = 0.017) and on day 7 (r = 0.471, P = 0.049), as well as between CRP and each of the admission serum endotoxin (r = 0.3, P = 0.03) and the intestinal permeability index (r = 0.375, P = 0.007).

CONCLUSIONS

In patients with acute pancreatitis, plasma concentrations of CTpr appear to reflect more closely the derangement in gut barrier function rather than the extent of systemic inflammation.

Hypocalcemia in patients with acute pancreatitis: a putative role for systemic endotoxin exposure

INTRODUCTION

Hypocalcemia is not uncommon during acute pancreatitis and is associated with a poor outcome. Whilst the mechanisms responsible for its development remain unclear, there is evidence to implicate endotoxemia in other models of sepsis.

AIM

To investigate the potential role of systemic endotoxin exposure in the development of hypocalcemia in patients with acute pancreatitis.

METHODOLOGY

Adjusted serum calcium was measured daily, and the lowest value within 72 hours of admission for acute pancreatitis was determined. Serum endotoxin and both IgG and IgM antiendotoxin core antibodies (EndoCAbs) were measured on admission. Attacks were classified as mild (n = 51) or severe (n = 21) according to the criteria of the Atlanta International Symposium of 1992.

RESULTS

Hypocalcemia was significantly more frequent (86% versus 39%, p < 0.001) and reached significantly lower levels during severe attacks than during mild attacks (median [interquartile range], 2.06 [1.78-2.17] mmol/L, versus 2.23 [2.15-2.30] mmol/L; p < 0.001). Endotoxemia was present in a significantly greater proportion of patients with severe disease (71% versus 41%; p = 0.037), and serum IgM and IgG EndoCAbs were significantly depleted during severe attacks in comparison with mild attacks (p = 0.007 and p = 0.039, respectively). A negative and significant correlation was observed between endotoxemia and both the admission and lowest serum concentrations of adjusted calcium (r = -0.424 and p = 0.022; r = -0.383 and p = 0.037, respectively), and the latter correlated significantly with serum IgG EndoCAb concentrations (r = 0.251; p = 0.036).

CONCLUSION

Systemic endotoxin exposure appears to play a significant role in the development of hypocalcemia in patients with acute pancreatitis.

Preoperative and intraoperative predictors of postoperative morbidity, poor graft function, and early rejection in 190 patients undergoing liver transplantation

HYPOTHESIS

Preoperative and intraoperative variables predict in part adverse outcome after liver transplantation.

DESIGN

Prospective, blinded, cohort study.

SETTING

Tertiary care hospital.

SUBJECTS

A total of 190 adult patients undergoing primary liver transplantation.

MAIN OUTCOME MEASURE

Adverse outcome was prospectively defined as either in-hospital death or prolonged postoperative hospitalization (>14 days) associated with morbidity. Potential preoperative and intraoperative risk factors were collected. Associations were tested by univariate analysis followed by multivariate analysis in which preoperative factors were entered before intraoperative factors.

RESULTS

Adverse outcome occurred in 44.7% of patients. Incidences of other complications were as follows: in-hospital mortality (8.4%), primary graft nonfunction (4.2%), poor early graft function (1.1%), and early rejection (31.2%). Univariate predictors of adverse outcome were United Network for Organ Sharing status (P =.003), Child-Turcotte-Pugh score (P =.02), POSSUM physiological score (P =.002), recipient age (P =.01), preoperative serum high-density lipoprotein cholesterol level (P =.03), preoperative serum creatinine level (P =.002), preoperative serum total IgG level (P =.004), duration in hospital preoperatively (P =.03), operative duration (P<.001), allogeneic erythrocyte transfusions (P<.001), total intraoperative fluids (P =.002), and use of inotropic agents (P =.01). In the final multivariate model, predictors of adverse outcome were United Network for Organ Sharing status (P =.03), recipient age (P =.002), and total intraoperative fluids (P =.04). Most patients who died or had a prolonged hospitalization exhibited dysfunction of more than 1 organ system, including pulmonary, renal, and infectious complications.

CONCLUSIONS

Adverse outcome occurs frequently after liver transplantation, usually involves multiple organ systems, and is predicted in part by several preoperative and intraoperative factors.

Endotoxin-neutralizing capacity of serum from cardiac surgical patients

OBJECTIVE

To determine if endotoxin core antibody (EndoCAb) from the serum of cardiac surgical patients neutralizes endotoxin in an ex vivo biologic assay.

DESIGN

Prospective blinded cohort study.

SETTING

Academic medical center.

PARTICIPANTS

Patients (n = 203) undergoing cardiac surgery.

INTERVENTIONS

Sera were obtained from patients preoperatively.

MEASUREMENTS AND MAIN RESULTS

EndoCAb levels were determined by enzyme-linked immunosorbent assay. Sera were incubated for 15 minutes at 37 degrees C with varying concentrations of endotoxin from a clinically relevant bacterium (Escherichia coli serotype O18), then tested for the presence of endotoxin activity using the validated Limulus amebocyte lysate assay. Median (interquartile range) IgM and IgG EndoCAb levels were 118 median units (range, 31 to 259 median units) and 208 median units (range, 108 to 401 medium units). Increasing levels of IgM EndoCAb were associated with increased neutralization of endotoxin (p < 0.0001). Increasing levels of IgG EndoCAb were associated with increased neutralization of endotoxin (p < 0.0001). An additive effect of IgM and IgG EndoCAb levels on endotoxin neutralization was observed without evidence of synergistic or plateau effects. EndoCAb levels did not completely predict serum neutralization capacity.

CONCLUSION

Anti-EndoCAbs of both classes (IgM and IgG) were able to neutralize lipopolysaccharide from a clinically relevant bacterium in an ex vivo model. Neither Igm nor IgG appeared to be more capable of neutralization in this model. These antibodies did not completely predict neutralization capacity; other endogenous factors in human serum must be capable of lipopolysaccharide neutralization.

Endotoxin, cytokines and lipid peroxides in children with intussusception

BACKGROUND

Intussusception is a relatively common paediatric surgical emergency. The aim of this study was to investigate selected inflammatory mediators in children with acute intussusception and to identify potentially useful plasma markers of clinical outcome.

METHODS

Clinical, radiographic, operative and pathological details were recorded prospectively of all children presenting to a single institution with a confirmed diagnosis of acute intussusception during 1 year. Paired acute and convalescent venous blood samples were collected in a standard manner for blinded analysis of the following: malondialdehyde, C-reactive protein (CRP), interleukin (IL) 6, neopterin, tumour necrosis factor alpha, endotoxin, and immunoglobulin (Ig) G and IgM antiendotoxin core antibody (EndoCAb).

RESULTS

Thirty-two consecutive children (23 boys, nine girls) with a median age of 4 months were studied. Acute ileocolic intussusception was managed by air enema reduction (n = 19), operative reduction (n = 8) or surgical resection (n = 5). Peripheral blood cultures were sterile. Acute levels of plasma IL-6, neopterin and CRP were significantly raised in comparison to both normal laboratory ranges and convalescent samples (P < 0.001). Using stepwise discriminant analysis, CRP was identified as the best variable at distinguishing between the three treatment groups (P < 0.001). IgM EndoCAb concentrations were significantly greater in the convalescent sera of all the patients (P < 0.001).

CONCLUSION

Acute ileocolic intussusception in childhood is associated with endotoxinaemia and significantly raised levels of circulating inflammatory cytokines. Plasma CRP at diagnosis showed a statistically significant positive correlation with disease severity.

Decreased endotoxin immunity is associated with greater mortality and/or prolonged hospitalization after surgery

BACKGROUND

Patients undergoing noncardiac surgery often develop postoperative morbidity, potentially attributable to endotoxemia and the systemic inflammatory response syndrome. Endogenous antibodies to endotoxin may confer protection from endotoxin-mediated toxicity. The authors sought to determine the association of preoperative antiendotoxin immunity and death or prolonged hospitalization in a broad population of general surgical patients undergoing major surgery.

METHODS

To test the hypothesis that low preoperative serum antiendotoxin core antibody (EndoCAb) concentration is an independent predictor of adverse outcome after general surgery, 1,056 patients undergoing routine noncardiac surgery were enrolled into a prospective, blinded, cohort study. Immunoglobulin M EndoCAb, immunoglobulin G EndoCAb, total inmunoglobulin M, and immunoglobulin G concentrations were measured in serum obtained preoperatively. A physiologic risk score using the established POSSUM criteria was assigned preoperatively to each patient. The primary predefined composite end point (postoperative complication) was either in-hospital death or postoperative length of stay greater than 10 days. Multivariate logistic regression was used to test the study hypothesis.

RESULTS

Overall, postoperative complication occurred in 234 of the 1,056 patients (22.1%). Lower immunoglobulin M EndoCAb concentration (P = 0.006) predicted increased risk of postoperative complication independent of POSSUM physiologic risk score (P < 0.001). In contrast, total immunoglobulin M and total immunoglobulin G concentrations did not predict adverse outcome. Complications involved multiple organ systems and were generally unrelated to the type or site of surgery, consistent with the systemic inflammatory response syndrome.

CONCLUSIONS

Adverse outcome after routine noncardiac surgery is common and is predicted in part by low concentrations of EndoCAb. The authors' findings suggest that endotoxemia may be a cause of postoperative morbidity after routine noncardiac surgery.

Preparation and preclinical evaluation of a novel liposomal complete-core lipopolysaccharide vaccine

Our objective is to develop a prophylactic vaccine strategy that can be evaluated for surgical and other high-risk hospitalized patients. In this paper, we describe the preparation and preclinical evaluation of a liposomal complete-core lipopolysaccharide (LPS) vaccine that is nontoxic and broadly antigenic. Complete-core (Ra-chemotype) LPSs were isolated from four gram-negative bacterial strains (Escherichia coli K-12, E. coli R1, Pseudomonas aeruginosa PAC608, and Bacteroides fragilis), mixed together to form a cocktail of complete-core LPSs, and then incorporated into multilamellar liposomes consisting of dimyristoyl phosphatidyl choline, dimyristoyl phosphatidylglycerol, and cholesterol in a 4:1:4 molar ratio. The endotoxic activities of these LPS-containing liposomes were less than 0.1% of the endotoxicities of the original free LPSs as measured by the Limulus amoebocyte lysate assay. In vivo administration of liposomal complete-core LPS mixed with Al(OH)(3) to rabbits resulted in no pyrogenicity or overt toxicity over a 7-day period. In immunoblots, sera from rabbits following active immunization elicited cross-reactive antibodies to a large panel of rough and smooth LPSs from numerous clinically relevant gram-negative bacteria, including E. coli (serotypes O1, O4, O6, O8, O12, O15, O18, O75, O86, O157, and O111), P. aeruginosa (Fisher-Devlin serotypes 1, 2, and 3, which correspond to International Antigenic Typing Scheme types 6, 11, and 2, respectively), Klebsiella pneumoniae (serotypes O1, O2ab, and O3), B. fragilis, and Bacteroides vulgatus. Active immunization of mice with liposomal complete-core LPS provided protection against a lethal challenge with E. coli O18 LPS. The vaccine tested was nontoxic, nonpyrogenic, and immunogenic against a wide variety of pathogens found in clinical settings.

Exposure to bacteroides fragilis endotoxin during cardiac surgery

Although endotoxemia has been observed during cardiac surgery, the identity of endotoxins to which patients are exposed is unknown. We tested the hypothesis that antibodies to Bacteroides fragilis (an anaerobic gut commensal and a common pathogen) decrease during cardiac surgery, thereby reflecting systemic exposure to this type of endotoxin. Serum antiendotoxin antibody levels were measured in 55 patients during routine cardiac surgery at the following times: Preoperatively, Pre-CPB (immediately before initiation of cardiopulmonary bypass [CPB]), Pre-CPB+5 (5 min after initiation of CPB), and End (end of surgery). Antiendotoxin antibody levels were determined by using enzyme-linked immunosorbent assay. Total immunoglobulin M (IgM) levels were measured by using laser nephelometry and decreases in total IgM levels were used to control changes in antiendotoxin antibody levels attributable to hemodilution. Median (interquartile range) hemodilution corrected IgM anti-B fragilis antibody levels decreased by 12% (5%-20%) from Preoperatively to End of surgery (P < 0.001). In contrast, median hemodilution corrected anti-B fragilis antibody levels did not change significantly from Pre-CPB to Pre-CPB+5, validating the correction for hemodilution. Immunoglobulin G anti-B fragilis antibody levels and IgM and immunoglobulin G anticore antibody levels decreased similarly during surgery. Intraoperatively, levels of anti-B fragilis endotoxin antibodies decreased significantly out of proportion to hemodilution. These results suggest that cardiac surgical patients are exposed to B fragilis endotoxin.

IMPLICATIONS

We prospectively measured hemodilution-corrected antiendotoxin antibody levels in 55 cardiac surgical patients. We observed significant decreases in hemodilution-corrected levels of antibody to both Bacteroides fragilis and the core of endotoxin.

Quality assurance by a commercial flow cytometry method of leucodepletion of whole blood donations: initial application of universal testing and proposals for a batch-release sampling plan

We have used the Becton-Dickinson LeucoCOUNT test to monitor residual leucocytes in whole blood by flow cytometry following leucodepletion filtration. This test was found to be quick, robust and reliable, and allowed measurement of residual leucocytes down to 2.25 x 104 leucocytes per unit, which was found to match approximately the limit of filter proficiency. The results of testing > 1000 units showed a lognormal distribution with means between log(10) 4.864 (0.73 x 105) and log(10) 5.016 (1.04 x 105) leucocytes per unit in the three different homogeneous groups of filtered units studied. The numbers of units with residual leucocytes exceeding the 5 x 106 upper threshold were 1/577, 2/457 and 0/87 in these groups. The filtration processes were validated according to the published BEST working party guidelines and were well within the 99% confidence and 95% tolerance target for the 5 x 106 upper threshold set for the UK. A sampling plan based on British Standard BS 6001 with elimination of outliers by the extreme studentized deviate (Grubbs' test) was evaluated on random samples from these groups and has been adopted locally as a prospective batch-release criterion for release of leucodepleted blood.

Lack of correlation between failure of gut barrier function and septic complications after major upper gastrointestinal surgery

OBJECTIVE

To determine the influence of abnormal gut barrier function on the risk of septic complications in patients undergoing major resectional surgery for upper gastrointestinal cancer.

SUMMARY BACKGROUND DATA

A failure of the gut mucosal barrier to exclude bacteria and endotoxin from the portal and systemic circulation is incriminated in the development of sepsis and multiple organ failure. Although the experimental data is compelling, corroborative evidence from studies in humans is sparse. This study attempted to correlate both preoperative gut barrier dysfunction and the pattern of change after surgery with septic outcome.

METHODS

Sixty-eight patients undergoing curative resectional surgery for upper gastrointestinal cancer were monitored for 30-day septic morbidity (intraabdominal abscesses/empyema and pneumonia). Intestinal permeability, serum IgM and IgG anti-endotoxin antibodies (EndoCAb), and serum C-reactive protein were measured before surgery and on postoperative days 1 and 7.

RESULTS

Increased intestinal permeability before surgery did not predict septic outcome. Major surgery was associated with increased intestinal permeability and evidence of endotoxin exposure. Comparing sepsis and nonsepsis groups, however, there was no significant difference in intestinal permeability, endotoxin exposure, and the acute phase response after surgery.

CONCLUSIONS

This study demonstrates that gut barrier dysfunction occurs after surgery, but the magnitude of change does not differentiate patients in whom sepsis develops and those in whom it does not. Preoperative increased intestinal permeability had no predictive value for sepsis. This study failed to support the thesis that gut barrier dysfunction is directly linked to sepsis.

Distribution of cell-associated prion protein in normal adult blood determined by flow cytometry

Leucocyte subpopulations from normally healthy individuals were identified by recognized combinations of fluorochrome-conjugated antibodies to CD markers and stained by different monoclonal antibodies (MAb) to normal cellular prion protein (PrPC), including the 3F4 MAb. Cell preparations were examined by three-colour flow cytometry. All mononuclear leucocyte subpopulations and platelets expressed PrPC, but polymorphonuclear leucocytes and red blood cells expressed little or no PrPC. The amounts of PrPC expressed by the different cells were calculated by comparison to bead standards. Mononuclear leucocytes expressed 3000-4000 molecules of antibody-reactive PrPC per cell. Resting platelets expressed around 1400 molecules of PrPC per cell, whereas activated platelets expressed around 4800 molecules of PrPC per cell. Extrapolation of these values to the amounts of the various cells in whole blood showed that platelet PrPC accounted for at least 96% of cell-expressed PrPC in blood. The PrPC on mononuclear cells and platelets was sensitive to enzymatic treatment of cells by proteinase k and phosphatidylinositol-specific phospholipase C. Certain anti-PrPC MAbs which showed equivalent intensity of staining to MAb 3F4 on fresh cells showed relative reductions of staining compared to MAb 3F4 on stored cells, indicating possible structural alterations of PrPC under these conditions.

Preliminary assessment of whole-blood, red-cell and platelet- leucodepleting filters for possible induction of prion release by leucocyte fragmentation during room temperature processing

Universal leucodepletion is being introduced in the U.K. to reduce a theoretical risk of Creutzfeldt-Jakob disease (CJD) transmission. If CJD infectivity is associated with leucocytes, any cell fragmentation associated with filtration could reduce the potential benefit. Four types each of whole blood, red cell and platelet leucodepletion filters were assessed after holding of blood units for at least 4 h at 22 degrees C. In all cases the mean residual leucocyte content was <1 000 000 per unit, with only two individual filtered whole blood units having a leucocyte content exceeding this. Evidence of leucocyte fragmentation during filtration was sought but not found by assay of soluble elastase, beta-thromboglobulin and normal prion protein, as well as by isotopic labelling of leucocyte external membrane. These preliminary studies indicate that it was possible to prepare leucodepleted blood components by filtration at room temperature, and that this appeared not to be associated with overt cell fragmentation. Definitive demonstration that fragmentation does not occur requires the development of improved general (non-specific) assays for cell membrane fragments.

Early increase in intestinal permeability in patients with severe acute pancreatitis: correlation with endotoxemia, organ failure, and mortality

Sepsis accounts for 80% of deaths from acute pancreatitis. This study aimed to investigate early changes in intestinal permeability in patients with acute pancreatitis, and to correlate these changes with subsequent disease severity and endotoxemia. The renal excretion of enterally administered polyethylene glycol (PEG) 3350 and PEG 400 was measured within 72 hours of onset of acute pancreatitis to determine intestinal permeability. Severity was assessed on the basis of APACHE II scores and C-reactive protein measurements. Serum endotoxin and antiendotoxin antibodies were measured on admission. Eight-five patients with acute pancreatitis (mild in 56, severe in 29) and 25 healthy control subjects were studied. Urinary excretion of PEG 3350 (median) was significantly greater in patients who had severe attacks (0.61%) compared to those with mild disease (0.09%) and health control subjects (0.12%) (P <0. 0001), as was the permeability index (PEG 3350/400 excretion) (P <0. 00001). The permeability index was significantly greater in patients who subsequently developed multiple organ system failure and/or died compared with other severe cases (0.16 vs. 0.04) (P = 0.0005). The excretion of PEG 3350 correlated strongly with endotoxemia (r = 0.8; P = 0.002). Early increased intestinal permeability may play an important role in the pathophysiology of severe acute pancreatitis. Therapies that aim to restore intestinal barrier function may improve outcome.

The effect of tacrolimus (FK506) on intestinal barrier function and cellular energy production in humans

BACKGROUND & AIMS

The maintenance of the intestinal mucosal barrier may be energy dependent. Tacrolimus is a potent immunosuppressive drug that decreases mitochondrial adenosine triphosphate production and increases intestinal permeability in animals.

METHODS

Twelve liver graft recipients receiving tacrolimus, 9 healthy volunteers, and 5 liver graft recipients not receiving immunosuppression underwent a combined absorption-permeability-mitochondrial function test using 5 g lactulose, 1 g L-rhamnose, 0.5 g D-xylose, 0.2 g 3-O-methyl-D-glucose, 1 mg/kg 2-keto[1-13C]isocaproic acid ([13C]KICA), and 20 mg/kg L-leucine. The respiratory quotient and resting energy expenditure were measured by indirect calorimetry. Tacrolimus pharmacokinetic profiles and levels of endotoxin and IgM and IgG endotoxin core antibodies were determined.

RESULTS

Tacrolimus inhibited the decarboxylation of [13C]KICA, the resting energy expenditure, and the respiratory quotient in an exposure-dependent manner, suggesting an inhibition of mitochondrial respiration. Tacrolimus inhibited intestinal absorptive capacity in an exposure-dependent manner. Tacrolimus-treated patients had an increased intestinal permeability and significantly higher endotoxin levels compared with healthy volunteers.

CONCLUSIONS

Tacrolimus inhibits cellular energy production in humans at clinically relevant doses. This is associated with an increased intestinal permeability, endotoxemia, and an impaired intestinal absorptive capacity.

Proinflammatory mediator activity, endogenous antagonists and the systemic inflammatory response in intra-abdominal sepsis. Scottish Sepsis Intervention Group

BACKGROUND

Severe intra-abdominal sepsis continues to carry a high mortality rate. The physiological response to sepsis in this condition and its relationship with proinflammatory mediators and their endogenous antagonists require further clarification.

METHODS

Fifty-seven patients were stratified by Acute Physiology And Chronic Health Evaluation (APACHE) II score at the time of admission to an intensive care unit (group 1, score of less than 20; group 2, score of 20 or more). Serial measurements of clinical and immunological variables were made.

RESULTS

Non-survivors from group 2 had a raised acute physiology score (P = 0.01), a higher peak serum interleukin (IL) 6 concentration (P = 0.03) and a depressed level of endogenous immunoglobulin (Ig) G class antiendotoxin core antibody (P = 0.005). In group 1, although organ failure score increased progressively in non-survivors, physiology score and peak IL-6 level were similar to those in survivors, and endogenous IgG class antiendotoxin core antibody titre rose (P = 0.02). In both groups IL-1 and tumour necrosis factor alpha were detected infrequently, but their natural antagonists were present in much higher concentrations in both survivors and non-survivors. Levels of C-reactive protein were raised in both but were not significantly different between survivors and non-survivors.

CONCLUSION

During the development of organ failure and death, the pattern of proinflammatory mediators and their endogenous antagonists can vary markedly and may in part be determined by the extent of the initial physiological disturbance.

Gut barrier function in malnourished patients

BACKGROUND

The integrity of the gastrointestinal mucosa is a key element in preventing systemic absorption of enteric toxins and bacteria. In the critically ill, breakdown of gut barrier function may fuel sepsis. Malnourished patients have an increased risk of postoperative sepsis; however, the effects of malnutrition on intestinal barrier function in man are unknown.

AIMS

To quantify intestinal barrier function, endotoxin exposure, and the acute phase cytokine response in malnourished patients.

PATIENTS

Malnourished and well nourished hospitalised patients.

METHODS

Gastrointestinal permeability was measured in malnourished patients and well nourished controls using the lactulose:mannitol test. Endoscopic biopsy specimens were stained and morphological and immunohistochemical features graded. The polymerase chain reaction was used to determine mucosal cytokine expression. The immunoglobulin G antibody response to endotoxin and serum interleukin 6 were measured by enzyme linked immunosorbent assay.

RESULTS

There was a significant increase in intestinal permeability in the malnourished patients in association with phenotypic and molecular evidence of activation of lamina propria mononuclear cells and enterocytes, and a heightened acute phase response.

CONCLUSIONS

Intestinal barrier function is significantly compromised in malnourished patients, but the clinical significance is unclear.

Increased intestinal permeability and altered mucosal immunity in cholestatic jaundice

OBJECTIVE

To examine the effects of cholestatic jaundice on gut barrier function.

SUMMARY BACKGROUND DATA

Gut barrier failure occurs in animal models of jaundice. In humans, the presence of endotoxemia indirectly implicates failure of this host defense, but this has not previously been investigated in jaundiced patients.

METHODS

Twenty-seven patients with extrahepatic obstructive jaundice and 27 nonicteric subjects were studied. Intestinal permeability was measured using the lactulose-mannitol test. Small intestinal morphology and the presence of mucosal immunologic activation were examined in endoscopic biopsies of the second part of the duodenum. Systemic antiendotoxin core IgG antibodies and serum interleukin-6 and C-reactive protein were also quantified. Intestinal permeability was remeasured in 9 patients 5 weeks after internal biliary drainage.

RESULTS

The median lactulose-mannitol ratio was significantly increased in the jaundiced patients. This was accompanied by upregulation of HLA-DR expression on enterocytes and gut-associated lymphoid tissue, suggesting immune activation. A significant increase in the acute phase response and circulating antiendotoxin core antibodies was also observed in the jaundiced patients. After internal biliary drainage, intestinal permeability returned toward normal levels.

CONCLUSIONS

A reversible impairment in gut barrier function occurs in patients with cholestatic jaundice. Increased intestinal permeability is associated with local immune cell and enterocyte activation. In view of the role of gut defenses in the modern paradigm of sepsis, these data may directly identify an important underlying mechanism contributing to the high risk of sepsis in jaundiced patients.

Conclusive evidence of endotoxaemia in biliary obstruction

BACKGROUND

Endotoxaemia is implicated in the pathophysiology of obstructive jaundice. The EndoCab enzyme linked immunosorbent assay (ELISA) is a novel assay which measures endogenous antibody (IgG) to the inner core region of circulating endotoxins (ACGA).

AIMS

To investigate the significance of endotoxaemia in biliary obstruction using the EndoCab assay and assess the specificity of the humoral response to endotoxin compared with an exogenous antigenic challenge (tetanus toxoid, TT).

METHODS

Three groups of adult male Wistar rats were studied: no operation, sham operation, and bile duct ligation for 21 days (BDL). In the second study, rats rats received prior immunisation with TT.

RESULTS

In the preliminary experiment, plasma ACGA was significantly increased in the BDL group (306.6 (18.3)% versus 119.9 (6.7)% and 105.2 (4.6)% in the sham and no operation groups, respectively; p < 0.001). Although the mean endotoxin concentration in the BDL group was greater than that in the control groups this was not significant. There was a strong positive correlation between ACGA and endotoxin concentrations (p = 0.0021). In the second study mean ACGA after 21 days of BDL was significantly elevated (267.1 (31.2)% versus 101.6 (21.2)% at baseline, p < 0.0001). ACGA was unaffected in the other two groups. TT antibody concentrations fell in all three groups; only in the BDL group was the fall significant (97.6 (5.3)% versus 78.8 (4.2)% at baseline, p < 0.05).

CONCLUSIONS

The specific rise in ACGA supports the hypothesis that endotoxin has an integral role in the pathophysiology of obstructive jaundice. The production of anticore glycolipid antibodies specifically reflects systemic endotoxaemia in this model. The EndoCab assay provides a novel, sensitive, and specific method for endotoxin detection.

Relationship between preoperative endotoxin immune status, gut perfusion, and outcome from cardiac valve replacement surgery

STUDY OBJECTIVE

Endotoxin is a powerful trigger of systemic inflammation. Since cardiac surgery exposes patients to endotoxemia, this study was set up to define the relationship between preoperative endogenous endotoxin immune status, gut perfusion, and outcome following cardiac valve replacement surgery.

DESIGN

Observational study.

SETTING

University hospital.

PATIENTS

Fifty-nine consecutive patients undergoing cardiac valve replacement.

MEASUREMENTS AND MAIN RESULTS

Blood was assayed for IgG and IgM endotoxin core antibody (EndoCAb) levels preoperatively, immediately postoperatively, and at 4 h and 24 h postoperatively. Intraoperative gut mucosal perfusion was assessed using gastric tonometry. Complications were assessed for groups above and below the median EndoCAb value of a healthy population (100 median units micro/mL). Of the 59 patients, 12 developed at least one of a set of predefined complications. Of these 12, all had preoperative levels of IgM EndoCAb below 100 MU/mL (p<0.025). Eleven had IgG EndoCAb levels below 100 MU/mL (0.05<p<0.1). There was no relationship between the fall in gastric intramucosal pH and exposure to endotoxin as implied by the fall in unbound IgM EndoCAb levels, although the specificity of tonometry for predicting complications could be improved by considering the patient's preoperative EndoCAb status.

CONCLUSIONS

Preoperative EndoCAb levels were related to poor outcome following cardiac surgery and may be used to improve the specificity of GI tonometry in predicting postoperative complications.

Priming of neutrophil respiratory burst activity by lipopolysaccharide from Burkholderia cepacia

Neutrophil activation may play an important role in the pathogenesis of respiratory disease in Burkholderia cepacia-colonized cystic fibrosis (CF) patients. As bacterial lipopolysaccharides (LPS) are potent immunostimulatory molecules, we investigated the role of B. cepacia LPS in neutrophil activation processes. LPS extracted from a highly transmissible and virulent strain of B. cepacia (J2315) was found to increase neutrophil surface expression of the beta2 integrin, complement receptor 3, and to prime neutrophil respiratory burst responses to the neutrophil-activating agent fMet-Leu-Phe. By contrast, LPS extracted from a nonmucoid Pseudomonas aeruginosa strain isolated from a patient with CF showed little or no priming activity. As B. cepacia is currently being developed as a biocontrol agent for large-scale agricultural release, we compared LPS molecules from a range of bacterial strains for their proinflammatory ability. Priming activity was demonstrated in LPS extracts from all B. cepacia strains tested, with one environmental strain, J2552, showing the highest activity. These findings indicate (i) that B. cepacia LPS may contribute to the inflammatory nature of B. cepacia infection in CF patients, both by promoting increased neutrophil recruitment and by priming neutrophil respiratory burst responses, and (ii) that environmental strains of B. cepacia may have considerable inflammatory potential in susceptible individuals.

Intramucosal acidosis and systemic host responses in abdominal aortic aneurysm surgery

OBJECTIVES

To assess the specific host responses to systemic endotoxemia and tumor necrosis factor (TNF) activation after abdominal aortic aneurysm surgery by measuring antiendotoxin core antibodies (EndoCab) immunoglobulin (Ig)G and IgM, and soluble p55TNF receptor concentrations. The role of the gut in initiating these immune responses was evaluated by correlating the systemic markers to changes in the intramucosal pH of the sigmoid colon.

DESIGN

Retrospective, reevaluation study.

SETTING

Vascular unit of a university hospital.

PATIENTS

Eleven patients who underwent abdominal aortic aneurysm repair surgery were selected from a larger patient cohort (n = 42) on the basis of their clinical outcome (four patients had fatal complications and seven patients had an uneventful recovery).

INTERVENTIONS

After induction of anesthesia, intramucosal pH of the sigmoid colon was measured using tonometry. Blood samples were obtained from indwelling catheters or direct venipuncture preoperatively, during surgery, and daily until postoperative day 5.

MEASUREMENTS AND MAIN RESULTS

Those patients who died developed intramucosal acidosis of the sigmoid colon intraoperatively. Significant consumption of both IgG and IgM EndoCab antibodies was found in all patients. By measuring the concentration of antibodies to a neutral antigen, i.e., tetanus toxoid, the consumption of IgG EndoCab antibody concentrations was shown to be a specific host response. In all patients, reciprocal changes in the serum concentrations of p55TNF receptor and interleukin (IL)-6 were observed. The percentage increase in p55TNF receptor and the concentration of IL-6 were significantly higher in the nonsurvivor group by 48 hrs. There were significant correlations between, intramucosal pH and EndoCab antibodies, intramucosal pH and p55 TNF receptor, and p55 TNF receptor and IL-6.

CONCLUSIONS

The development of colonic ischemia is associated with a significant consumption of IgG EndoCab antibodies and a simultaneous increase in soluble p55TNF receptor. This study provides further support for the concept that gut-derived endotoxin and the generation of TNF may play a role in the pathogenesis of complications after abdominal aortic aneurysm surgery.

1997 Harry M. Vars Research Award. Does the route of feeding modify gut barrier function and clinical outcome in patients after major upper gastrointestinal surgery?

BACKGROUND

Direct experimental evidence suggests that total enteral nutrition (TEN) reduces septic morbidity compared with bowel rest and total parenteral nutrition (TPN) and that mucosal support and maintenance of gut barrier function is a key mechanism. This effect is supported indirectly by clinical studies, but this question has not previously been investigated directly in the postoperative patient. This study examined the hypothesis that early enteral feeding after major upper gastrointestinal surgery may modulate gut barrier function and decrease the risk of major infective complications compared with bowel rest and parenteral nutrition.

METHODS

A randomized clinical trial of 67 patients (TPN = 34; TEN = 33) fed postoperatively for 7 days was performed. Thirty-day major morbidity and mortality were monitored. Intestinal permeability was measured using the lactulose/mannitol test preoperatively and on postoperative days 1 and 7. Systemic anti-endotoxin core immunoglobulin G and M antibodies and serum albumin and C-reactive protein were quantified at these time points.

RESULTS

No clinical benefit was observed in patients fed enterally compared with the parenterally fed group. Intestinal permeability was increased on the 1st postoperative day in association with evidence of endotoxin exposure. By day 7, enteral feeding compared with parenteral feeding had failed to significantly influence any of the gut barrier or systemic parameters.

CONCLUSIONS

This randomized controlled trial of TEN vs TPN after major upper gastrointestinal surgery failed to show a clinical benefit for the enteral route. Moreover, enteral nutrition did not modulate gut barrier function postoperatively.

Endotoxin antibodies in African sleeping sickness

Antibodies to the core region of endotoxin (endotoxin core antibodies, EndoCAb), which cross-react with endotoxin from a range of Gram-negative bacteria, are maintained in relative homeostasis in health, but undergo marked changes in a number of different diseases associated directly or indirectly with endotoxaemic or septicaemic states. The levels of EndoCAb IgG in the blood and cerebrospinal fluid (CSF) of 35 late-stage sleeping sickness patients and 9 control individuals were measured by ELISA. EndoCAb levels were significantly elevated in the patient blood (mean EndoCAb value 290 MU/ml cf. control 182 MU/ml, P < 0.001), and CSF (mean EndoCAb value 254 MU/ml cf. control 150 MU/ml, P < 0.001). EndoCAb IgG levels correlated with endotoxin levels in patient blood (r = 0.78, P < 0.001), but not in the CSF and were not reduced 6 weeks following chemotherapy, unlike the endotoxin levels. It is concluded that late-stage sleeping sickness is associated with chronic exposure to endotoxins from Gram-negative bacteria.

Relationship of preoperative antiendotoxin core antibodies and adverse outcomes following cardiac surgery

OBJECTIVE

To test the hypothesis that low serum antiendotoxin core antibody (EndoCAb) level is an independent predictor of adverse outcome following cardiac surgery.

DESIGN

Prospective, blinded, cohort study.

SETTING

Tertiary care medical center.

SUBJECTS

A total of 301 patients undergoing coronary artery bypass graft surgery and/or valvular heart surgery.

DESIGN

Preoperative serum was assayed for IgM EndoCAb, IgG EndoCAb, total IgM, and total IgG levels. Known preoperative risk factors were assessed, and patients were assigned a risk score using a validated method.

MAIN OUTCOME MEASURE

A major complication, defined as either in-hospital death or postoperative length of stay greater than 10 days.

RESULTS

Overall, a major complication occurred in 34 patients (11.3%). Lower IgM EndoCAb level independently predicted (P=.002) increased risk of major complication over and above the effects of preoperative risk score (P=.02), total IgG level (P=.07), and all other known perioperative risk factors. In contrast, IgG Endo-CAb and total IgM concentrations did not predict outcome. No association existed between risk score and level of IgM EndoCAb.

CONCLUSION

There is marked preoperative variability in humoral immunity against endotoxin core, which is not accounted for by differences in known preoperative risk factors. In this study, low levels of IgMEndoCAb were an important independent predictor of adverse postoperative outcome, which supports the theory that endotoxemia is a cause of postoperative morbidity.

Passive immunisation with IgG endotoxin core antibody hyperimmune fresh frozen plasma

Postoperative complications have been associated with low pre-operative endotoxin core antibody (EndoCAb) status. Seventy-three patients scheduled to undergo elective cardiac surgery were screened for IgG EndoCAb levels 1 week prior to admission. Of these 73 patients, 39 had levels below the median of a healthy population (100 MU = median units/ml). Only 6 received an infusion of IgG EndoCAb hyperimmune fresh frozen plasma (FFP) due to surgical rescheduling or unavailability of compatible hyperimmune FFP. The 6 patients demonstrated significant elevation (p < 0.0001) of their IgG EndoCAb levels from a mean level of 43 MU/ml (range: 26-75) to a posttransfusion mean of 267 MU/ml (range: 227-300), which persisted until at least immediately prior to the operative period. We conclude that passive immunisation with EndoCAb hyperimmune FFP is possible prior to elective surgery and that the kinetic profile of such an administration will allow the FFP to be given the night prior to surgery and still maintain significantly elevated levels for surgery planned the following morning.

Sump bay fever: inhalational fever associated with a biologically contaminated water aerosol

OBJECTIVE

To investigate the clinical, serological, and environmental features of a work related inhalational fever associated with exposure to an aerosol generated from a biologically contaminated 130,000 gallon water pool in a building used for testing scientific equipment.

METHOD

Cross sectional survey of all exposed subjects (n = 83) by symptom questionnaire, clinical examination, spirometry, and serology for antibody to Pseudomonads, pool water extract, and endotoxin. In symptomatic patients diffusion capacity was measured, and chest radiology was performed if this was abnormal. Serial peak flow was recorded in those subjects with wheeze. Bacterial and fungal air sampling was performed before and during operation of the water pool pump mechanism. Endotoxin was measured in the trapped waters and in the pumps. Serum cotinine was measured as an objective indicator of smoking.

RESULTS

Of the 20 symptomatic subjects, fever was most common in those with the highest exposure (chi 2 42.7, P < 0.001) in the sump bay when the water was (torrentially) recirculated by the water pumps. Symptoms occurred late in the working day only on days when the water pumps were used, and were independent of the serum cotinine. Pulmonary function was normal in most subjects (spirometry was normal in 79/83, diffusion capacity was low in five subjects, chest radiology was normal). Peak flow recording did not suggest a work relation. The bacterial content of the aerosol rose from 6 to > 10,000 colony forming units per cubic metre (cfu/m3) (predominantly environmental Pseudomonads) when the pumps were operating. High endotoxin concentrations were measured in the waters and oil sumps in the pumps. Low concentrations of antibody to the organisms isolated were detected (apart from two subjects with high antibody) but there was no relation to exposure or the presence of symptoms and similar antibody was found in the serum samples from a non-exposed population. The fever symptoms settled completely with the simple expedient of changing the water and cleaning the pumps.

CONCLUSION

Given the results of our study, the development of inhalational fever in this unique environment and clearly restricted cohort was closely related to the degree of exposure to contaminated aerosol and mainly occurred in the absence of distinct serological abnormality and independent of cigarette smoking.

Natural cytokine antagonists and endogenous antiendotoxin core antibodies in sepsis syndrome. The Sepsis Intervention Group

OBJECTIVE

To assess the value of measuring circulating concentrations of mediators (endotoxin, tumor necrosis factor-alpha [TNF-alpha], interleukin-1 beta [IL-1 beta], and interleukin-6[IL-6]) and their endogenous antagonists (antiendotoxin core antibody [EndoCAb], interleukin-1 receptor antagonist [IL-1ra], and soluble TNF receptors [sTNF-R]) in predicting mortality and organ failure in sepsis syndrome.

DESIGN

Cohort study with a follow-up period of 30 days.

SETTING

Intensive therapy units of five tertiary referral centers in Scotland.

SUBJECTS

A total of 146 intensive therapy unit patients with sepsis syndrome underwent repeated sampling during a 10-day period following admission to an intensive therapy unit.

MAIN OUTCOME MEASURES

Circulating concentrations of mediators and antagonists were compared in survivors and nonsurvivors.

RESULTS

Median Acute Physiology and Chronic Health Evaluation II score was 23 (range, 8 to 40). Mortality at 30 days was 49%. On entry to the study, circulating endotoxin was detected in 66% of patients, TNF-alpha in 14%, and IL-1 beta in 29%. Levels did not predict mortality or organ failure. Patients with IL-6 concentrations in excess of 3000 pg/mL had an increased mortality rate (64% vs 40%, P = .02). The incidence of IgG EndoCAb depletion on entry to the study was 26% in nonsurvivors and 10% in survivors (P = .02). Initial concentrations of both type I and type II sTNF-R were significantly higher in nonsurvivors (P < .01). Initial circulating IL-1ra concentrations were not of value in predicting mortality. Cytokine antagonists were present in concentrations 30- to 100,000-fold greater than their corresponding cytokine.

CONCLUSION

The observed high circulating levels of the cytokine antagonists IL-1ra and sTNF-R and the relatively small proportion of patients developing EndoCAb depletion may contribute to the limitations of therapies that aim to augment natural defenses against endotoxin or the proinflammatory cytokines.

Significance of systemic endotoxaemia in inflammatory bowel disease

Quantitative and qualitative disturbances in faecal flora suggest a role for enteric bacteria and their products in the pathogenesis of inflammatory bowel disease (IBD). This study investigated the hypothesis that systemically circulating endotoxins are of pathogenic significance in IBD by measuring antibody, cytokine, and acute phase protein responses. Systemic endotoxaemia was found in 88% patients with ulcerative colitis (n = 25) and 94% with Crohn's disease (n = 31) during clinical relapse. Systemic endotoxaemia correlated positively with anatomic extent and clinical activity of ulcerative colitis. Circulating tumour necrosis factor (TNF) was detected in 40% of patients with ulcerative colitis and 45% with Crohn's disease. Plasma TNF concentrations correlated with clinical and laboratory measures of disease activity and were associated with a surgical outcome to the disease episode. Plasma soluble TNF receptor p55 concentration correlated positively with disease activity and endotoxin core antibody concentrations. Plasma IgG endotoxin core antibody concentrations were significantly increased in patients with Crohn's disease and correlated with systemic endotoxaemia. The presence of systemic endotoxaemia, its correlation with disease activity, disease extent, and endotoxin core antibody concentration and the detection of circulating TNF and soluble TNF receptors all support a pathogenic role for endotoxins in IBD.

Prophylactic use of human endotoxin-core hyperimmune gammaglobulin to prevent endotoxaemia in colostrum-deprived, gnotobiotic lambs challenged orally with Escherichia coli

The efficacy of human IgG polyclonal antibody to endotoxin-core in preventing endotoxaemia and subsequent disease was studied in colostrum-deprived gnotobiotic lambs challenged orally at about 5 h old with 10(9) cfu Escherichia coli. Human endotoxin-core hyperimmune gammaglobulin was given intravenously to 5 lambs at 1.9 g IgG/kg bodyweight prior to challenge. Human albumin was given intravenously to 3 control lambs. Bacteraemia was observed in all lambs, but the incidence was lower (P < 0.01) and the onset later (P < 0.05) in gammaglobulin pre-treated lambs. These lambs showed no signs of disease, whereas clinical endotoxaemia, manifesting as watery mouth disease, was diagnosed in 2 of the 3 control lambs which were killed between 18 and 22 h after challenge. Thus, prophylactic treatment of colostrum-deprived lambs with human IgG enriched in endotoxin-core antibodies was effective in reducing the degree of bacteraemia and preventing endotoxaemia, leukopenia and clinical disease following oral challenge with E. coli.

Lack of effect of recombinant platelet-derived growth factor on human neutrophil function

Platelet-derived growth factor (PDGF) has been reported to induce chemotaxis, degranulation, and superoxide anion generation, and to increase the expression of CD11b/CD18 in human neutrophils; hence, it has been proposed as an important regulator of neutrophil function. Most of the studies on PDGF, however, have been complicated by the use of nonrecombinant PDGF or the use of mixed leukocyte cell preparations. Assessment of the effects of recombinant human PDGF-AB or -BB which display agonist activity against both PDGF receptor subtypes failed to demonstrate any effect of this peptide on neutrophil shape change, respiratory burst activity, CD11/CD18, or CD62-L expression, inositol 1,4,5-trisphosphate accumulation, or phosphorylation of mitogen-activated protein kinase. This apparent lack of effect of PDGF was consistent with our findings that neutrophils display no specific 125I-PDGF-AB or -BB binding and lack detectable mRNA for PDGF alpha-receptor and beta-receptors. These data indicate that human neutrophils do not possess functional PDGF receptors and question previous reports of a functional effect of this peptide in these cells.

Lack of effect of recombinant platelet-derived growth factor on human neutrophil function

Platelet-derived growth factor (PDGF) has been reported to induce chemotaxis, degranulation, and superoxide anion generation, and to increase the expression of CD11b/CD18 in human neutrophils; hence, it has been proposed as an important regulator of neutrophil function. Most of the studies on PDGF, however, have been complicated by the use of nonrecombinant PDGF or the use of mixed leukocyte cell preparations. Assessment of the effects of recombinant human PDGF-AB or -BB which display agonist activity against both PDGF receptor subtypes failed to demonstrate any effect of this peptide on neutrophil shape change, respiratory burst activity, CD11/CD18, or CD62-L expression, inositol 1,4,5-trisphosphate accumulation, or phosphorylation of mitogen-activated protein kinase. This apparent lack of effect of PDGF was consistent with our findings that neutrophils display no specific 125I-PDGF-AB or -BB binding and lack detectable mRNA for PDGF alpha-receptor and beta-receptors. These data indicate that human neutrophils do not possess functional PDGF receptors and question previous reports of a functional effect of this peptide in these cells.

Anti-bacteroides lipopolysaccharide IgG levels in healthy adults and sepsis patients

Members of the genus Bacteroides greatly outnumber enterobacteria in the human colon and therefore represent a vast potential pool of biologically active LPS. An enzyme-linked immunosorbent assay was developed to estimate the distribution of IgG levels to LPS from B. fragilis, B. vulgatus, B. thetaiotaomicron and to a mixture of rough LPS from three enterobacteria and Pseudomonas aeruginosa in sera from 641 adult blood donors. By inhibition ELISA some cross-reactivity was demonstrated between the different anti-bacteroides LPS IgG, but with very little between the anti-bacteroides LPS IgG and the anti-enterobacterial/Pseudomonas LPS IgG. Serum IgG was measured daily over 5-9 day periods in 12 sepsis patients (6 survivors, 6 non-survivors) and in a healthy individual. In all patients IgG levels fluctuated to a greater extent than levels in a healthy subject. Variations all followed similar overall trends and indicated that exposure to bacteroides LPS had occurred. In 5 out of 6 survivors, IgG levels were rising at the end of the period, while 4 of the 6 non-survivors showed falls, with an exception showing increasing levels to B. fragilis LPS. In 5 out of 6 non-survivors, IgG levels against B. fragilis LPS were substantially higher than those against the other LPSs. In this small sample some trends in antibody kinetics have been recognised which suggest bacteroides LPS may be significant in sepsis, and indicate that this study should be extended.

Tumor necrosis factor induction by an aqueous phenol-extracted lipopolysaccharide complex from Bacteroides species

The stimulation of macrophages and monocytes by lipopolysaccharide (LPS) results in the secretion of tumor necrosis factor (TNF), a cytokine which is thought to play a pivotal role in subsequent host responses. Its induction is thought to be facilitated by the binding of complexes of LPS and LPS-binding protein to CD14. The LPS of Bacteroides species was considered a weak endotoxin; however, in a recent study we have shown that the biological activity and chemical composition of the LPS from Bacteroides species are dependent on the extraction method. The present study determines the capacity of LPS extracted by aqueous phenol (the method for producing an LPS of high endotoxic activity) from four species of Bacteroides to induce TNF. Induction was investigated from human mononuclear leukocytes (MNL), THP-1 cells (with and without enhancement by vitamin D2 for CD14), and peritoneal macrophages from C3H/HeJ (LPS nonresponder) and C3H/HeN (LPS responder) mice. Escherichia coli O18K- LPS, a typical smooth LPS of heterogeneous molecular mass, was used as a control throughout. The stimulation of TNF production by E. coli LPS was between two- and fourfold more than that by Bacteroides LPS in MNL, in THP-1 cells (with enhancement for CD14), and in peritoneal macrophages from C3H/HeN mice. In THP-1 cells (without enhancement for CD14), there was no significant difference in TNF production between E. coli and Bacteroides LPSs. In peritoneal macrophages from C3H/HeJ mice, E. coli LPS stimulated no TNF production, but there was no significant difference in TNF production from peritoneal macrophages from C3H/HeJ and C3H/HeN mice by Bacteroides LPS. In all cell populations, there was a peak of TNF production after approximately 4 h of stimulation with all LPSs tested. However, other peaks of TNF production were seen in MNL and THP-1 cells (with enhancement for CD14) after stimulation with E. coli LPS only. In stimulation assays in which Bacteroides LPS was together with but in excess of E. coli LPS, it was found that TNF production from MNL and THP-1 cells (with and without enhancement for CD14) was comparable to that of Bacteroides LPS alone and not E. coli LPS alone. An anti-CD14 monoclonal antibody did not inhibit Bacteroides LPS-stimulated TNF production. However, E. coli LPS-stimulated TNF release was inhibited by an anti-CD14 monoclonal antibody, most noticeably in MNL and THP-1 cells (with enhancement for CD14).(ABSTRACT TRUNCATED AT 400 WORDS)

A re-appraisal of the biological activity of bacteroides LPS

Lipopolysaccharides (LPS) were extracted from seven Bacteroides strains by three different techniques: the phenol-water (PW), phenol-chloroform-petroleum (PCP) and Triton-Mg2+ methods. The strains selected included two different B. fragilis strains, one of which was grown in two different media. Yields varied between the strains, growth media and extraction technique, but generally the highest yield by weight was from the PCP method and the lowest from the PW method. The PW method was selected for the greatest amounts of carbohydrate and KDO, and the PCP method for the least. Phosphorus levels were more uniform among all extraction methods. Protein contamination was found in all Bacteroides LPS extracts, with extremely low levels in PW-LPS and the highest levels in material extracted by the PCP and Triton-Mg2+ techniques. No protein contamination could be detected after proteinase K treatment. After silver staining LPS PAGE profiles showed ladder patterns characteristics of smooth LPS for B. vulgatus, B. thetaiotaomicron and the control Escherichia coli O18:K- strains, whereas the other Bacteroides strains showed mainly rough and low M(r) material only. The PCP method did not select for high M(r) material in the B. fragilis strains; otherwise the LPS profiles for all extraction methods were identical. The biological activities of native and sodium salt form LPS were investigated on a weight for weight basis and compared to that of E. coli O18:K- PW-LPS. Amongst the LPS from Bacteroides strains, those prepared by the PW method were found to have a significantly higher activity in a galactosamine mouse lethality model, in induction of TNF and the Limulus amoebocyte lysate (LAL) assay, than LPS extracted by the PCP or Triton-Mg2+ methods. LPS from Bacteroides strains extracted by the PCP method had consistently low activity in all assays. Comparing PW-LPS from Bacteroides strains with that from E. coli O18:K- in the galactosamine mouse model, the E. coli O18:K- LPS was c. 5000-fold more active than the most active bacteroides LPS. However, in the LAL assay native PW-LPS from both the B. fragilis strains, and B. caccae had higher activities (up to 30-fold) than E. coli O18:K- LPS, with the PW-LPS from the other Bacteroides spp. being up to 15-fold less active than the E. coli O18:K- PW-LPS. In the TNF induction assay, E. coli O18:K- PW-LPS was 4-50-fold more active than bacteroides PW-LPS.(ABSTRACT TRUNCATED AT 400 WORDS)

Modulation of immune function and weight loss by L-arginine in obstructive jaundice in the rat

Jaundiced surgical patients have a high incidence of postoperative complications. Many causative factors have been identified including cachexia and immune suppression. The amino acid L-arginine has anabolic and immunostimulatory properties. It was hypothesized that dietary supplementation with L-arginine would diminish the weight loss and immune suppression of obstructive jaundice. Sixteen male Wistar rats rendered jaundiced by bile duct ligation were allocated to two groups. The test group (n = 8) received drinking water supplemented with 1.8 percent L-arginine ad libitum and the control group (n = 8) received a solution of isonitrogenous glycine. Both groups had free access to standard chow. Body-weight, and fluid and food intake were recorded. After 21 days, delayed-type hypersensitivity to 2,4-dinitrofluorobenzene was assessed. Animals receiving L-arginine consumed more food than controls (mean(s.e.m.) 414(16) versus 360(13) g, P < 0.05) and lost less weight (mean(s.e.m.) proportion of initial body-weight lost 7.8(1.2) versus 14.8(1.4) percent, P < 0.05). The delayed-type hypersensitivity response was significantly greater in rats receiving L-arginine (mean(s.e.m.) increase in ear thickness 23.9(2.7) versus 9.4(2.1) percent, P < 0.05). In this animal model of obstructive jaundice dietary supplementation with L-arginine diminished both weight loss and immune suppression.

Antibodies to endotoxin core in sudden infant death syndrome

To assess the possible role of endotoxaemia in the pathogenesis of sudden infant death syndrome (SIDS), antibodies to endotoxin core (EndoCAb), which have previously been shown to be depressed by systemic endotoxaemia, were measured. IgG and IgM EndoCAb and total serum IgG and IgM were measured in serum samples from 25 children who had died from SIDS and 164 control children under 1 year of age. Twelve (48%) of the 25 children who had died from SIDS had no detectable IgG EndoCAb compared with 28 (17%) of the 164 control children, and this difference was concentrated in children aged less than 3 months. There was no significant difference between the two groups in the percentage of children with no IgM EndoCAb, nor in the total IgG and IgM concentrations. For IgM EndoCAb, the younger children who had died from SIDS had higher concentrations than the controls. These results suggest that, in children who have died from SIDS, due to either unusually early or severe exposure to endotoxin, maternal IgG EndoCAb have been depleted and early IgM EndoCAb triggered.