Insights into the mechanisms of defective antigen presentation after hemorrhage

Although hemorrhage depresses macrophage antigen presentation (AP), a critical component in eliciting an antigen-specific immune response, it is not known which particular step in macrophage AP (i.e., uptake, ingestion, catabolism, or presentation of degraded antigens to T cells) is defective. To study this, C3H/HeN mice were bled to an arterial mean blood pressure of 35 mm Hg, maintained for 60 minutes, and then adequately resuscitated. Peritoneal and splenic macrophage cultures were prepared 2 and 24 hours after hemorrhage. Macrophage AP capacity was measured by coculturing macrophages with the T-helper cell clone D10.G4.1. To gain information about macrophage ability to digest the specific antigen conalbumin, lysosomal activity was bypassed by use of chemically denatured conalbumin peptides. To study macrophage ability to present conalbumin peptides, macrophages were fixed and D10.G4.1 proliferation in response to fragmented conalbumin was determined. AP of native conalbumin by peritoneal macrophages and splenic macrophages was depressed (p less than 0.05) by 50% (peritoneal macrophages) and 55% (splenic macrophages) 2 hours and 57% (peritoneal macrophages) and 35% (splenic macrophages) 24 hours after hemorrhage. In contrast, presentation of conalbumin peptides was only slightly decreased. In addition, the ability of fixed peritoneal macrophages and splenic macrophages to present conalbumin peptides was similar in hemorrhaged and sham mice. Because bypassing of macrophage lysosomal activity with degraded native antigens prevented the suppression of AP, the results suggest that hemorrhage-induced suppression of AP is not caused by a reduced macrophage capacity to present antigenic peptides but by decreased antigen catabolism by macrophages.     

Prostaglandin E2 depresses antigen-presenting cell function of peritoneal macrophages

Eicosanoids play a prominent role in trauma. Such mediators of inflammation negatively influence cell-mediated immunity (CMI). There is, however, no information available on the effect of eicosanoids on a critical event in CMI, i.e., antigen-presenting (AP) cell function of macrophages (M luminal diameter), a cellular process responsible for the activation of T and B lymphocytes. The aim of this study, therefore, was to examine the effect of prostaglandin E2 (PGE2) and thromboxane B2 (TXB2) on AP cell function of the peritoneal M luminal diameter. To study this, a T-helper-cell clone, D10.G4.1 was employed. This cell clone proliferates in the presence of Iak (Class II glycoprotein, MAC product) bearing M luminal diameter and specific antigen (conalbumin A) thus directly reflecting the AP capability of the M luminal diameter. Peritoneal M luminal diameter were harvested from B10.BR mice (H2k) and their AP was tested in vitro by incubating varying numbers of M luminal diameter with 2 X 10(4) D10.G4.1 cells/well and conalbumin (400 micrograms/ml) in the presence and absence of different concentrations of PGE2 or TXB2. Cultures were incubated for 72 hr, pulsed with [3H]-thymidine, and harvested. At concentrations of 10, 30, and 100 nM of PGE2, D10.G4.1 proliferations were 38, 35, and 20% of control, respectively (P less than 0.05 compared to control). TXB2 added at the above-mentioned concentrations did not suppress the proliferative response of D10. Thus, PGE2 but not TXB2 has a potent immunosuppressive effect on AP of peritoneal M luminal diameter.(ABSTRACT TRUNCATED AT 250 WORDS)     

Mechanism of immunosuppression following hemorrhage: defective antigen presentation by macrophages

The mechanism by which simple hemorrhage profoundly impairs the proliferative response of T lymphocytes to mitogen and alloantigen, produces a defect in interleukin-2 generation, and increases the susceptibility to sepsis remains unknown. Since antigen presentation (AP) by the macrophage (M phi) plays a critical role in the antigen-specific activation of T-helper cells and lymphokine production, we investigated whether the function of the M phi as an AP cell is altered following hemorrhage. C3H/HEJ mice were bled to a mean BP of 35 mm Hg, maintained at that level for 1 hr, and then resuscitated. There was no mortality with this model. Control mice were not bled but otherwise treated identically. Immediately after resuscitation the mice were sacrificed and peritoneal M phi (PM phi) as well as splenic adherent cells (SAC) were harvested. AP function was tested by coculturing different numbers of PM phi and SAC with D10.G4.1 cells (2 x 10(4) cells/well) in the presence of conalbumin (300 micrograms/ml). This T-helper cell clone proliferates upon recognition of conalbumin in the context of Iak (a M phi surface membrane glycoprotein), thus directly reflecting M phi AP capability. After 72 hr of incubation, the cultures were pulsed with [3H]thymidine and harvested. D10.G4.1 proliferations induced via AP by PM phi and SAC from hemorrhaged-resuscitated mice were 29 and 24% of control, respectively (P less than 0.05). Thus, we conclude that AP by M phi following hemorrhage is defective despite adequate resuscitation, a mechanism which could explain the state of immunosuppression and enhanced susceptibility to sepsis.     

Immunoprotective effect of a calcium channel blocker on macrophage antigen presentation function, major histocompatability class II antigen expression, and interleukin-1 synthesis after hemorrhage

Hemorrhage induces a severe suppression of the immune system resulting in increased susceptibility to sepsis. Although studies indicate beneficial effects of calcium channel blockers on cell and organ functions after low-flow conditions, it remains unknown whether such agents have any effects on different immune responses after hemorrhage. To study this, C3H/HeN mice were bled to a mean blood pressure of 35 mm Hg and were maintained for 60 minutes, followed by resuscitation with their own shed blood and adequate fluid. The mice received either the water-soluble calcium channel blocker diltiazem (400 or 2400 micrograms/kg body weight) or saline solution (vehicle). Peritoneal macrophages were obtained by lavage 24 hours later. Antigen presentation was measured by coculturing peritoneal macrophages with the D10.G4.1 helper T-lymphocyte clone. Immune associated antigen (Ia) expression was determined by direct immunofluorescence. Interleukin (IL)-1, 6, and tumor necrosis factor-alpha (TNF) levels in peritoneal macrophage supernatants were measured by use of cytokine-specific cellular assays. Hemorrhage caused a significant decrease in peritoneal macrophage antigen presentation function, Ia expression, and IL-1 and IL-6 synthesis in the vehicle-treated group, whereas TNF levels were increased. However, both doses of diltiazem significantly improved peritoneal macrophage antigen presentation, Ia expression, and IL-1 synthesis. IL-6 synthesis was only increased with high doses of diltiazem, whereas both diltiazem doses decreased TNF production. These results indicate that the calcium channel blocker diltiazem can markedly improve macrophage functions after hemorrhage. The use of diltiazem might offer a new therapeutic modality in the treatment of immunosuppression and in decreasing the susceptibility to sepsis after hemorrhagic shock.     

Effects of laparotomy on systemic macrophage function.

Surgical trauma induces immunosuppression that may adversely influence survival. This study examined the effect of laparotomy on two different macrophage populations, peritoneal macrophages (PM phi) and Kupffer cells. Female, 6- to 8-week old, CFW/C3H-HeN mice (n = 160) were randomly allocated to one of three study groups: control, ether anesthetic only, or ether anesthetic and laparotomy. On postoperative days 1 and 3, PM phis and Kupffer cells were harvested and assayed for superoxide anion production (O2-), percent macrophage phagocytosis of Candida albicans (CAP), percent C. albicans killed by macrophages (CAK), percent major histocompatibility complex (MHC)-class II antigen expression, and antigen presentation. Macrophages isolated on postoperative day 1 were also cocultured with 100 units/10(6) cells/ml interferon-gamma (IFN-gamma). Laparotomy significantly impaired microbicidal activity (O2-, percent CAP, and percent CAK) and antigen presentation on postoperative day 1. On postoperative day 3, O2- and antigen presentation were increased significantly (p less than 0.05) over control values, indicating a rebound phenomenon. Kupffer cell microbicidal function was unchanged on postoperative days 1 and 3. The initial immune impairment (PM phis: O2-, CAP, and CAK) was abrogated by IFN-gamma treatment. In immunosuppressed hosts after injury, administration of macrophage-activating factors such as IFN-gamma could be of therapeutic benefit.     

Defective antigen presentation to a cloned T helper cell by macrophages from burned mice can be restored with interleukin-1

T helper (Th) cell dysfunction occurring very early (i.e., 24 to 72 hours) after a 30% full-thickness burn in a murine model cannot be attributed to suppressor T cell activity. Th cell activity is influenced by the activity of antigen-presenting cells (APCs). These cells process antigen and present a complex of antigen and cell surface Ia to the T cell. Additionally, they elaborate interleukin-1 (Il-1), and these events lead to Th cell release of Il-2, expression of Il-2 receptors, and proliferation of Th cells. We examined the contribution of APCs to postburn Th cell dysfunction by using mitomycin C-treated spleen cells from normal and burned mice as an APC population. The Th cell population consisted of a cloned Th cell line (D10.G4.1) that recognizes conalbumin in the context of I-Ak and proliferates when approximately stimulated. We found that APCs from burned mice induced significantly less Th cell proliferation (p less than 0.05). This was true of unfractionated spleen cells (50.4% of control) as well as positively selected (44.2% of control) or negatively selected (51.9% of control) splenic APCs. When cocultured with APCs from control mice, APCs from burned mice did not suppress control values of Th cell proliferation. Finally, the addition of murine Il-1 in vitro to cultures of burn-derived APCs, antigen, and T cell clone restored Th cell proliferation to control levels (from 38.3% to 92.8%) without nonspecifically enhancing similar cultures employing normal APCs. Il-1 in vitro did not improve Th cell function in the absence of antigen. Thus splenic APCs from mice exhibit defective antigen presentation early after burn injury. This defect is not a result of suppressor factor production by burn APCs and can be restored by Il-1 in vitro. Th cell dysfunction early after burn injury is thus due, in part, to APC dysfunction.     

Effect of blood transfusion on antigen presentation function and on interleukin 2 generation

To study the effect of blood transfusion (BT) on cell-mediated immunity, we examined the antigen presentation function of peritoneal macrophages and interleukin 2 (IL-2) generation by splenocytes. C3H/HEJ mice were transfused with 0.2 mL of fresh allogeneic blood obtained from C57BL/6 mice; they were killed on days 1, 3, and 7 after BT. A second group of C3H/HEJ mice was transfused with 0.2 mL/d of the same allogeneic blood on three successive days; they were killed on day 7 following the last BT. The antigen presentation function of peritoneal macrophages was measured by utilizing a D10.G4.1 T-helper cell clone; IL-2 activity in supernatants of concanavalin A-stimulated splenocytes was tested by utilizing an IL-2-dependent HT-2 cell line. The results indicate that although antigen presentation function remains unaffected after single and multiple BTs, the ability of splenocytes to generate IL-2 decreases significantly even after a single BT. Thus, the increased susceptibility to infection and the additional immune perturbations in malignant neoplasms following BT may be due in part to decreased IL-2 generation.     

Energetics of defective macrophage antigen presentation after hemorrhage as determined by ultraresolution 31P nuclear magnetic resonance spectrometry: restoration with adenosine triphosphate-MgCl2.

BACKGROUND. The purpose of this study was to determine whether a decrease in macrophage energetics contributes to the profound immune dysfunction that occurs after hemorrhage and, if so, whether adenosine triphosphate (ATP)-MgCl2 treatment has any beneficial effects on the above parameters. METHODS. C3H/HeN mice were bled to a mean blood pressure of 35 mm Hg, maintained at that pressure for 60 minutes, resuscitated with their own shed blood and Ringer's lactate, and treated with ATP-MgCl2 (80 mumol/kg body weight) or saline solution (vehicle). Peritoneal macrophages were harvested 1 hour after resuscitation and ATP levels were determined by 31P nuclear magnetic resonance spectrometry. In addition, macrophage functions were determined by measuring antigen presentation capacity (AP), as well as interleukin-1 (IL-1), interleukin-6 (IL-6), and tumor necrosis factor (TNF) synthesis. RESULTS. Hemorrhage caused a significant decrease in peritoneal macrophage AP function, as well as IL-1, IL-6, and TNF synthesis, by 52% +/- 14%, 91% +/- 12%, 78% +/- 8%, and 89% +/- 8%, respectively, which was correlated with a 78% +/- 6% decrease in macrophage ATP levels (p less than 0.05). Treatment with ATP-MgCl2 after hemorrhage restored macrophage ATP levels (p less than 0.05) and significantly increased (p less than 0.05) macrophage AP, IL-1, IL-6, and TNF release by 110% +/- 21%, 130% +/- 38%, 124% +/- 17%, and 66% +/- 24%, respectively. CONCLUSIONS. The decreased macrophage ATP levels may be the cause of defective macrophage AP and cytokine release after hemorrhage, and both macrophage ATP levels and macrophage immune functions can be restored with adjuvant ATP-MgCl2 treatment after hemorrhage.     

Effects of interleukin-1 (IL-1) on postsurgical macrophage secretion of protease and protease inhibitor activities.

Although peritoneal macrophages secrete a variety of inflammatory mediators and proteases during postsurgical repair of the peritoneum, regulation of this secretion is poorly understood. Here, the responsivity of peritoneal macrophages to interleukin-1 (IL-1) stimulation in vitro, measured by the secretion of protease and protease inhibitor activities, was evaluated as a function of postsurgical time. Macrophages were harvested at various times after peritoneal sidewall abrasion, isolated by discontinuous density centrifugation and cultured with varying concentrations of IL-1. IL-1 increased the secretion of plasminogen activator (PA) activity by peritoneal macrophages in a concentration-dependent manner on postsurgical Days 0, 3, 10, and 14. Macrophages harvested on postsurgical Day 1 after surgery responded only to high concentration of IL-1, while on Days 5 and 7 all doses of IL-1 stimulate PA. On Days 7, 10, and 14 after surgery, the secretion of PA activity (after acid treatment) by postsurgical macrophages was generally high and increased with IL-1 treatment. The level of PA activity after inactivation of acid labile inhibitors (PAI) also increased in a dose-dependent manner on Days 0, 3, and 5. Although Day 1 macrophages expressed the highest PAI activity of all groups, they had relatively low responsivity to IL-1 with regards to PAI secretion. The level of elastase activity by postsurgical macrophages was lowest on Day 1, highest on Day 7, and decreased thereafter. All concentrations of IL-1 inhibited elastase activity of macrophages on Day 7.(ABSTRACT TRUNCATED AT 250 WORDS)     

Kinetics of interleukin-1 secretion by murine macrophages recovered from the peritoneal cavity after surgery

Macrophages play a central role in wound healing after surgical injury possibly through the secretion of soluble factors like interleukin-1 (IL-1). IL-1 has many biological activities which regulate most of the cell types that appear in postsurgical wounds. In this study, we determined the levels of IL-1 production by murine macrophages harvested from postsurgical exudate at several time points after standardized peritoneal surgery. To further characterize the level of functional activities of postsurgical macrophages, the IL-1 levels were determined with or without stimulating the cells with lipopolysaccharide (LPS) and phorbol myristate acetate (PMA). After surgery, the number of macrophages harvested by peritoneal lavage increased, reached peak levels on Postsurgical Day 3, and then decreased. IL-1 levels secreted by macrophages cultured without stimuli gradually increased after surgery, reaching peak levels on Day 10. In conditioned media from LPS-PMA-stimulated macrophages, IL-1 levels were significantly greater than in media from unstimulated macrophages and peaked on Postsurgical Day 3. These data suggest that the susceptibility of postsurgical macrophages to stimuli changes during the postsurgical wound healing process. Accordingly, IL-1 may play an important role in the late rather than in the early phase of peritoneal repair.     

Do female sex steroids adversely or beneficially affect the depressed immune responses in males after trauma-hemorrhage?

HYPOTHESIS: Administration of female sex steroids in males after trauma-hemorrhage has salutary effects on the depressed immune responses. DESIGN: Randomized laboratory experiment. INTERVENTIONS: Male C3H/HeN mice were subjected to midline laparotomy and hemorrhagic shock (35+/-5 mm Hg for 90 minutes, then resuscitation) or sham operation and received subcutaneous 17beta-estradiol (40 microg/kg body weight) or corn oil vehicle at the beginning of resuscitation. MAIN OUTCOME MEASURES: At 24 hours after hemorrhage, the animals were killed and plasma 17beta-estradiol and IL-6, splenocyte interleukin (IL) 2, IL-3, and IL-10 production as well as splenic and peritoneal macrophage IL-1beta, IL-10, and IL-6 release were measured. RESULTS: Splenocyte IL-2 and IL-3 release were significantly depressed after hemorrhage in vehicle-treated mice (P<.05, analysis of variance). Treatment with 17beta-estradiol after hemorrhage led to the restoration of splenocyte IL-2 and IL-3 release. The depressed proinflammatory cytokine (IL-1 and IL-6) release seen in splenic and peritoneal macrophages was restored in the 17beta-estradiol-treated hemorrhage group. In contrast, the sustained release of the anti-inflammatory cytokine IL-10 by splenocytes and splenic and peritoneal macrophages in vehicle-treated mice after hemorrhage was decreased in 17beta-estradiol-treated mice. The increase in circulating IL-6 levels after hemorrhage was significantly attenuated in 17beta-estradiol-treated mice. Although administration of 17beta-estradiol increased plasma 17beta-estradiol levels by approximately 100% in sham as well as hemorrhage groups, improved immune responses were seen only in posthemorrhage 17beta-estradiol-treated mice. There was no adverse effect of 17beta-estradiol treatment in the sham or posthemorrhage groups. CONCLUSION: Since administration of a single dose of 17beta-estradiol in males after trauma-hemorrhage restores the immune functions and decreases circulating levels of IL-6, hormones with estrogenic properties should be considered as safe and novel therapeutic agents for restoring the immune responsiveness in male trauma victims.     

The hemostatic effect of deacetylated chitin membrane on peritoneal injury in rabbit model

In this study, we determined the effect of 80% deacetylated chitin (DAC-80) membrane on postsurgical bleeding after visceral and parietal peritoneal abrasion. Japanese white rabbits underwent a midline laparotomy followed either by a bilateral peritoneal sidewall abrasion (4×4 cm) or an abrasion of liver surface (3×2 cm). The injured surface was then covered with a 0.2 mm thick DAC-80 membrane. On postsurgical day 2, the rabbits were sacrificed and the amounts of postsurgical bleeding was determined by quantitating the number of red blood cells recovered in 50 ml peritoneal lavage fluid. The DAC-80 membrane was found to reduce postsurgical bleeding after the abrasion of liver surface (treated with DAC-80 membrane: 2.9±0.8; control: 24.6±5.9×10⁸ cells/peritoneal cavity, P<0.005). This same hemostatic activity was not observed after application in the peritoneal sidewall abrasion model. We also measured plasminogen activator activity (PA) and urokinase inhibitory (PAI) activity in the spent culture media of macrophages recovered from the postsurgical peritoneal exudate. The DAC-80 membrane reduced the PA secretion from postsurgical macrophages after liver surface abrasion (treated with DAC-80: 2.8±0.7; control: 3.9±0.9 mPU/ml). The DAC-80 membrane also showed similar effects on PA secretion after peritoneal sidewall abrasion. No significant effects were found in the secretion of PAI by postsurgical macrophages in both surgical models.These findings suggest that the DAC-80 membrane may have hemostatic activity through the modulation of fibrinolytic activity of peritoneal exudative macrophages.     

Kinetics of interleukin-1 and tumor necrosis factor secretion by rabbit macrophages recovered from the peritoneal cavity after surgery

Macrophages play a crucial role in wound healing after surgical injury, both as scavenger cells responsible for wound debridement and as cells that secrete soluble factors such as interleukin-1 (IL-1) and tumor necrosis factor (TNF). IL-1 and TNF alter many of the biological activities of cells that appear in postsurgical wounds. In this study, we determined the kinetics of IL-1 and TNF production by rabbit macrophages harvested from postsurgical peritoneal exudate (postsurgical macrophages) at several time points after peritoneal surgery. To further characterize the level of functional activities of postsurgical macrophages, the IL-1 and TNF levels were determined with or without stimulating the cells with lipopolysaccharide (LPS) and phorbol myristate acetate (PMA). After surgery, the number of macrophages harvested by peritoneal lavage increased, reached peak levels on postsurgical day 3, and then decreased. IL-1 levels secreted by macrophages cultured without stimuli were elevated on postsurgical day 14 compared to the values on day 3 and 7. TNF concentrations peaked on days 1 and 14. In the conditioned culture media from LPS-PMA-stimulated macrophages, the levels of both IL-1 and TNF peaked on postsurgical days 3 and 14. These data suggest that the susceptibility of postsurgical macrophages to stimuli changes during the wound healing process with maximum sensitivity to the stimuli present during the early phase of peritoneal repair (day 3).     

A role of postsurgical macrophage activation by peritoneal injury]

At a site of peritoneal injury after abdominal surgery, macrophages are thought to be a principle type of inflammatory cells. Therefore, we determined the metabolic activities of postsurgical peritoneal exudate macrophages using standardized rabbit model. Rabbits underwent midline laparotomy followed by resection and reanastomosis of the ileum. At various days after surgery, peritoneal exudate macrophages were recovered from lavage fluid. Postsurgical Day-5 macrophages expressed significantly high potential to produce superoxide anion even without PMA stimulation compared to non-surgical control macrophages, although an activity of Day-10 macrophages was similar to control. The conditioned media from postsurgical Day-1 macrophage culture strongly inhibited urokinase type plasminogen activator (PA) and this plasminogen activator inhibitor (PAI) activities decreased following the extension of postsurgical time. Conversely, PA activities of macrophage-conditioned media decreased by day 1 and then gradually increased reaching control levels by day 10. Elastase activities of macrophage-conditioned media gradually decreased until postsurgical day 10. These data suggest that surgical injury activates postsurgical exudate macrophages. However, a time course of metabolic activities of these cells was dependent upon each secretory products. This differential secretion might express the stage of activation and differentiation of postsurgical macrophages. Moreover, postsurgical activated macrophages may control the tissue repair through a digestion of injured matrix and fibrinolytic process.     

Interferon-gamma attenuates hemorrhage-induced suppression of macrophage and splenocyte functions and decreases susceptibility to sepsis.

Although it is known that interferon-gamma synthesis and macrophage functions are depressed after hemorrhage, it remains to be determined whether systemic administration of interferon-gamma has any effect on hemorrhage-induced depression of macrophage and splenocyte functions. To study this, C3H/HEN mice were bled to a mean blood pressure of 35 mm Hg, maintained for 60 minutes, and followed by adequate fluid resuscitation. The mice then received either 1000 units interferon-gamma or saline solution (vehicle). Peritoneal (pM phi) and splenic (sM phi) macrophages and splenocytes were isolated 24 hours later. PM phi antigen presentation was measured by coculturing pM phi with the D10.G4.1 cell clone. Major histocompatibility complex class II (Ia) antigen expression was determined by direct immunofluorescence. Cytokine release by pM phi, sM phi, and splenocytes was assessed with specific bioassays. For survival studies, mice were subjected to sepsis 3 days after hemorrhage. Treatment with interferon-gamma restored (p less than or equal to 0.05) hemorrhage-induced suppression of pM phi antigen presentation capacity and Ia antigen expression and increased (p less than or equal to 0.05) interleukin-1 and tumor necrosis factor release by pM phi and sM phi, as well as splenocyte proliferation (p less than or equal to 0.05). Interferon-gamma also decreased (p less than or equal to 0.007) the susceptibility to sepsis after hemorrhage. Thus interferon-gamma represents a potent agent for treating hemorrhagic shock-induced immunosuppression and for increasing the ability of the host defense system to combat bacterial infections after hemorrhage.     

Inflammatory response and bacterial dissemination afterlaparotomy and abdominal CO2 insufflation in a murine model of peritonitis

Background The immunologic repercussions due to cavity insufflation are the focus of great discussion. The aim of this study was to compare the inflammatory response and bacterial dissemination after laparotomy and abdominal CO₂ insufflation in a murine model of peritonitis. Methods Swiss mice were inoculated intraperitoneally with 0.5 ml of a solution containing 1 × 10⁸ colony-forming units (CFU)/ml of Escherichia coli and were divided into three groups as follow: control (anesthesia for 30 min), laparotomy (2.5-cm midline incision for 30 min), and CO₂ pneumoperitoneum (CO₂ cavity insufflation for 30 min). The number of leukocytes, CFU/ml counting, and the levels of interleukin (IL)-6, tumor necrosis factor-α (TNF-α), and IL-10 were evaluated in blood, peritoneal, and pleural fluid samples obtained at 90 min and 18 h after the procedures. Results The laparotomy group showed a greater bacterial dissemination to the blood, peritoneum, and pleural cavity and also greater neutrophil migration to the peritoneal cavity compared to the CO₂ insufflated and control groups. The 24-h mortality was also significantly higher in the laparotomy group. The IL-6 levels showed a precocious rise in all groups submitted to bacterial inoculation at the 90-min time point. At the 18-h time point, IL-6 levels in the peritoneum were significantly higher in the laparotomy group than in the control or CO₂ insufflated groups. At the same time, TNF-α levels were higher in the laparotomy and CO₂ insufflated groups than in controls; IL-10 levels showed no differences among the groups. Conclusions Our results suggest that cavity insufflation with CO₂ is a more effective method of access, inducing less bacterial dissemination and also a less intense inflammatory response. Cavity insufflation with CO₂ may present a good option for the surgical treatment of patients with bacterial peritonitis.     

Aluminum concentrations in serum, dialysate, urine and bone among patients undergoing continuous ambulatory peritoneal dialysis (CAPD)

Aluminum (Al) concentration in serum, urine, and dialysate was estimated in 21 patients undergoing continuous ambulatory peritoneal dialysis (CAPD). In 12 of the patients bone Al concentration was measured as well. Mean serum Al level was 32.4 +/- 21.0 micrograms/l. The Al concentrations in the dialysate and urine were 9.1 +/- 4.1 micrograms/l and 52.5 +/- 47.3 micrograms/l, respectively. Bone Al concentration was 21.0 +/- 14.9 ppm and correlated significantly with concentrations of Al in serum (p less than 0.01) and dialysate (p less than 0.01). A mass transfer (MT) from the patients to the dialysate was observed in all patients (-44.0 +/- 28.8 micrograms/24 h). There was a highly significant correlation between peritoneal Al MT and serum Al (p less than 0.001), actual Al consumption (p less than 0.05) and bone Al concentration (p less than 0.005) supporting the existence of an overflow phenomenon. Despite very low Al levels in the dialysate, patients are at risk of elevated Al levels in the serum, dialysate, urine and bone because of consumption of Al-containing phosphate binders.     

Effect of CO2 pneumoperitoneum on the systemic and peritoneal cytokine response in a LPS-induced sepsis model

We studied the effect of carbon dioxide (CO2) pneumoperitoneum on the systemic and peritoneal cytokine response in a rat model of intraperitoneal sepsis. After intraperitoneal injection of bacterial lipopolysaccharide (LPS, 10 mg/kg), rats were divided into 3 groups (n = 49 in each group): control (abdominal puncture); CO2 pneumoperitoneum, and laparotomy. Blood and peritoneal lavage fluid (PLF) were sampled at 0, 1, 2, 3, 4, 6, and 8 h after LPS challenge. Blood cell counts, plasma endotoxin level, and the levels of tumor necrosis factor-alpha (TNF-alpha), interleukin-1beta (IL-1beta), and interleukin-6 (IL-6) in the plasma and PLF were measured. Blood cell counts did not differ between the 3 groups. Plasma endotoxin levels in the pneumoperitoneum group were significantly increased immediately after the procedure (p < 0.05). Although peak plasma TNF-alpha levels in the pneumoperitoneum group were seen immediately after the procedure, other changes in plasma cytokine levels did not differ significantly between the 3 groups. PLF TNF-alpha and IL-1beta levels in the pneumoperitoneum group were significantly lower than levels in the control and laparotomy groups soon after the procedure (p < 0.05). PLF IL-6 levels in the pneumoperitoneum group tended to be lower than those in the laparotomy group. In conclusion, CO2 pneumoperitoneum might induce different responses between systemic and peritoneal cytokines soon after the procedure in a rat model of intraperitoneal sepsis.     

Macrophage antigen presentation and interleukin 1 production after cecal ligation and puncture in C3H/HeN and C3H/HeJ mice

Following cecal ligation and puncture with a 25-gauge needle, endotoxin-sensitive C3H/HeN mice have a 45% mortality compared with no mortality in endotoxin-resistant C2H/HeJ mice. Macrophage production of interleukin 1 and antigen presentation were studied in these two strains of mice following cecal ligation and puncture at 2, 4, 8, 16, and 24 hours and at 2, 4, 6, and 8 days. Splenic macrophages were cultured with a T-helper cell clone (D10.G4.1), and antigen presentation and interleukin 1 production were measured by D10.G4.1 proliferation. Macrophage antigen presentation by C2H/HeJ mice was markedly increased compared with that in C3H/HeN mice at all times after cecal ligation and puncture, most strikingly at 2 days (185m740 cpm for C3H/HeJ mice vs 30,300 for C2H/HeN mice). Macrophage interleukin 1 production was significantly increased in C3H/HeJ mice vs C3H/HeN mice at all times after cecal ligation and puncture (except at 2 days) and was maximal at 8 days (25,000 cpm for C3H/HeJ mice vs 5190 for C3H/HeN mice). These data suggest that the differences in mortality after cecal ligation and puncture between these two strains of mice may relate to a supranormal response of macrophages of C3H/HeJ mice or to an inadequate response of macrophages of C3H/HeN mice.