Prevention of Liver Reticuloendothelial Systemic Host Defense Failure after Surgery by Intravenous Opsonic Glycoprotein Therapy

Depression of the reticuloendothelial system (RES) was observed in rats following operative trauma consisting of laparotomy and jejunal enterotomy. This RES depression was manifested as a significant impairment in the phagocytic clearance of intravenously injected blood-borne test colloid mediated by a decline in hepatic Kupffer cell phagocytosis. Reticuloendothelial systemic host defense depression was correlated with a significant decline in bioassayable and immunoreactive opsonic α₂SB glycoprotein concentration over a 1-3 hr postoperative period with rebound elevation in opsonic activity by 24 hr postsurgery. Intravenous administration of purified opsonic α₂SB glycoprotein at the end of the operation prevented postoperative opsonic deficiency and restored normal hepatic RES phagocytic function. These studies coupled with previous observations in patients following surgery or after severe multiple trauma suggest that reticuloendothelial depression during and after operation mediated by opsonic deficiency may lead to a precarious imbalance between systemic host defense and the dissemination of blood-borne foreign and effete particulate matter such as injured platelets, fibrin microaggregates and immune complexes. Immunoreactive serum opsonic α₂SB glycoprotein determinations may serve as a valuable index of hepatic RE clearance capacity and opsonin therapy may potentially be a selective means to augment systemic host defense.     

Disturbances in circulating opsonic activity in man after operative and blunt trauma

A humoral factor deficit (α-2-opsonic glycoprotein) important for reticuloendothelial (RE) phagocytosis has been previously identified in animals as a major etiologic mechanism for RE host defense failure following trauma or operation. Assessment of this opsonic factor in man during the 72-hr period following extensive multiple trauma (n = 20) and major elective surgery (n = 13) revealed a transient depression of this opsonic protein at 24-hr postinjury in both surgical patients and surviving multiple trauma patients. Recovery of normal opsonic activity occurred by 48–72 hr postinjury in both groups. Nonsurviving multiple trauma patients had very low levels of circulating opsonic activity with no tendency toward recovery. The influence of an overnight fast in both preoperative patients (n = 8) and normal volunteers (n = 9) did not adversely affect the level of this humoral factor. Recovery of normal opsonic activity occurred during the 72-hr postoperative period, a time of diminished calorie intake, suggesting that a brief nutritional deficit is not solely responsible for postoperative RE depression. Altered RE function in patients following multiple trauma and major elective surgery may have important consequences in terms of the intravascular clearance of blood-borne particulate material such as platelet aggregates, fibrin, microthrombi, and other potentially noxious substances.     

Reticuloendothelial failure in chronic intra-abdominal sepsis: the role of opsonic fibronectin

Severe sepsis leads to depression of the reticuloendothelial (RE) system with delayed bloodstream clearance of particulate matter and bacteria. Fibronectin may be an important opsonin of the RE system and low fibronectin levels often accompany severe sepsis in man. We have investigated the effect of prolonged intra-abdominal sepsis on plasma fibronectin concentrations and RE function. Serial plasma fibronectin concentrations were determined in rabbits for 2 weeks after either the induction of sepsis (appendix abscess) (n = 6) or laparotomy only (n = 6). RE function was measured at 2 weeks by determining the clearance kinetics and organ distribution of low dose technetium tin colloid (TTC). There was an early transient depression in plasma fibronectin values followed by elevated concentrations at 48-72 h which were more marked in the sepsis group. There was a delay in the blood clearance with reduced hepatic and increased bone uptake of TTC. We conclude that depletion of opsonic fibronectin is unlikely to be an important factor contributing to the impairment of RE function associated with intra-abdominal sepsis and that RE depression in septic animals is due to intrinsic Kupffer cell dysfunction.     

Liver and spleen phagocytic depression after peripheral ischemia and reperfusion.

Liver and spleen phagocytic clearance of blood-borne microparticulate tissue debris and products of intravascular coagulation after trauma and surgical injury is an important mechanism to limit the deposition of debris in the pulmonary vascular bed. Plasma fibronectin (pFn) modulates this clearance process. We evaluated the effect of a localized peripheral ischemia and reperfusion injury on liver and spleen phagocytic function. Male rats (250 to 350 g) underwent 4 hours of tourniquet-induced bilateral hindlimb ischemia, followed by 18 hours of reperfusion after release of the tourniquet. Rats subjected to ether anesthesia alone or anesthesia followed by groin incision without ischemia were the control and sham groups, respectively. Reticuloendothelial (RE) phagocytic function was assessed at 15 minutes and 18 hours after the start of reperfusion by the in vivo liver and spleen removal of blood-borne iodine 125 (125I)-test microparticles, which were coated with gelatin (denatured collagen) to enhance their interaction with pFn. Liver and spleen particle uptake in control and sham rats was similar. In contrast, after 4 hours of ischemic injury with 15 minutes of reperfusion, we observed a 30% to 40% decrease (p less than 0.05) in liver and spleen particle uptake as compared with sham controls with partial restoration of this removal mechanism by 18 hours. This depression in liver and spleen phagocytic function was associated with a significant (p less than 0.05) increase in the deposition of the 125I-test particles in the lung. RE depression was not due to a deficiency of pFn; indeed, a marked elevation (588 +/- 12 micrograms/mL versus 1,083 +/- 40 micrograms/mL) of pFn was observed by immunoassay over the 18-hour reperfusion interval. Comparative bioassay of humoral (opsonic) versus cellular (Kupffer's cell) activity revealed that Kupffer's cells in livers from controls or ischemia-reperfusion rats exhibited normal phagocytic function when incubated in plasma harvested from either control or 4-hour ischemic rats. The opsonic activity of plasma harvested after ischemia and reperfusion was also more than adequate, consistent with the immunoassay analysis. Thus, the impaired liver and spleen clearance mechanism after peripheral ischemia and reperfusion injury did not appear to be due to either a macrophage cellular deficit or a lack of pFn. This clearance depression may be mediated by splanchnic malperfusion, which is known to develop after peripheral ischemia and reperfusion and associated soft tissue injury.     

Effect of hydroxyethyl starch, oxypolygelatin and human albumin on the phagocytic function of the reticuloendothelial system in healthy subjects

RES phagocytic function was determined in healthy volunteers prior to and up to 5 h after application of 10 ml/kg body weight of 6% hydroxyethyl starch (450,000; 0.7), 5.5% oxypolygelatin (30,000), or 5.0% human albumin solution. Phagocytosis (phagocytic index K) was evaluated in vivo by intravascular lipid clearance (Lipofundin clearance test). Immediately after infusion, the phagocytic rate increased by 30% in the hydroxyethyl starch group (n = 10; p less than 0.05), 14% in the oxypolygelatin group (n = 10; ns), and 24% in the albumin group (n = 8; ns). 2 h after infusion phagocytosis was still increased by 35% in the hydroxyethyl starch group (n = 10; p less than 0.05), by 18% in the oxypolygelatin group (n = 10; ns), and 13% in the albumin group (n = 8; ns). 5 h after infusion, K values had returned to normal in the albumin group (n = 4), but were still increased by 40% in the hydroxyethyl starch group (n = 4; ns). No statistically significant differences could be established among the 3 groups. The increase in the phagocytic rate, particularly after application of hydroxyethyl starch, might be explained by a dilution effect.     

Intraabdominal sepsis: effects on polymorphonuclear leukocyte Fc receptor-mediated phagocytosis

In vitro studies have shown that phagocytic cells are capable of undergoing activation in response to inflammatory signals and that the activation process is quite complex. A relationship between polymorphonuclear leukocyte (PMN) Fc receptor-mediated phagocytosis and oxidative metabolism has been seen in humans. We have sequentially examined circulating polymorphonuclear leukocytes (PMNs) from a total of 13 postoperative swine with either no sepsis, untreated intraabdominal sepsis, or treated intraabdominal sepsis to determine phagocytic activity over 8 postoperative days (POD). Products of the oxidative burst (i.e., myeloperoxidase) reduced the phagocytic activity of nonseptic swine PMN. Phagocytic activity was augmented by inhibiting the nonseptic swine oxidative burst with 10 mM sodium azide (an inhibitor of myeloperoxidase). In swine with untreated intraabdominal sepsis, PMN Fc receptor-mediated phagocytosis exhibited a biphasic response. An initial (between POD1 and POD4) increase in PMN function was followed by a subsequent (between POD4 and POD8) decrease in PMN function. Partial preservation of phagocytic capability was seen when swine were reexplored on POD4 and had their intraabdominal sepsis treated. These results indicate that (1) as in humans, nonseptic swine PMN Fc receptor-mediated phagocytosis is augmented by inhibition of the PMN respiratory burst; (2) untreated intraabdominal sepsis produces an initial increase and subsequent decrease in PMN Fc receptor-mediated phagocytosis; (3) early treatment of intraabdominal sepsis results in partial restoration of PMN Fc receptor-mediated phagocytosis.     

Deficits in reticuloendothelial humoral control mechanisms in patients after trauma.

Plasma opsonic activity as expressed by an alpha-2-globulin which stimulates hepatic Kupffer cell phagocytosis, and thus modulates RES clearance, was determined in patients at varying intervals following whole-body trauma. Plasma opsonic activity decreased markedly following trauma in both nonsurviving (NS) and surviving (S) trauma patients as compared to an age- and sex-matched group of healthy volunteers. The initial post-traumatic hypoopsonemia (0-72 hr) was more severe (p less than 0.01) in nonsurviving patients than surviving patients. Survivors following trauma manifested restoration of opsonin levels with a definite transient rebound hyperopsonemia during the recovery phase (11-30 days); nonsurviving patients exhibited persistent systemic alpha-2-globulin opsonic deficiency. On the basis of previous animal and human studies, the presently observed humoral deficits following trauma in patients could contribute to impairment of reticuloendothelial Kupffer cell clearance of blood-borne particulate matter such as fibrin, damaged platelets, and other altered autologous tissue. The importance of post-trauma RES dysfunction to survival following severe injury warrants further investigation and clinical consideration.     

Differential effects of portal diversion on hepatocyte function (HF) and hepatic reticuloendothelial cell (HRES) activity in the dog

End-to-side portocaval shunts (PCS) were constructed in six dogs to evaluate the effect of complete portal blood flow diversion on hepatocellular structure and function, hepatic reticuloendothelial (RE) activity, and serum opsonic activity (OA). RE activity remained normal after PCS despite a 40% reduction in estimated hepatic blood flow. Tissue distribution of injected colloid shifted away from liver to spleen, lung, and bone marrow. OA decreased to 40% of baseline values 6 weeks after PCS and remained low. Postshunt changes in hepatic morphology primarily affected hepatocytes and included deglycogenation and loss of rough endoplasmic reticulum. Significant changes in Kupffer cell morphology were not observed. Complete portal flow diversion in the dog caused profound alterations in hepatocellular structure and function without compromising Kupffer cell phagocytic and metabolic activity. Kupffer cells may be less dependent than hepatocytes upon hepatotrophic factors contained in portal blood. OA did not correlate with changes in vascular lipid clearance, suggesting that either phagocytosis of RES test lipid in the dog is not dependent on prior opsonization, or that the assay used was neither sensitive nor specific enough to measure a critical opsonic threshold required for effective phagocytosis.     

Reticuloendothelial Clearance of Blood-borne Particulates: Relevance to Experimental Lung Microembolization and Vascular Injury

The rapid increase in sheep lung vascular permeability observed during Pseudomonas aeruginosa bacteremia may be due to embolization of the pulmonary microvasculature by bloodborne particulates. Since alterations in lung microvascular permeability during mild septicemia in sheep may reflect inefficient RES phagocytic clearance of bacteria as well as products of bacterial induced intravascular coagulation, the opsonic and phagocytic aspects of RES function in sheep (30-50 kg) were compared to other species. RES function was evaluated by both the clearance and relative organ uptake of gelatinized I¹³¹ RE test lipid emulsion and gelatinized colloidal carbon. Immunoreactive opsonic a₂SB glycoprotein levels were determined by electroimmunoassay. The phagocytic index for RES clearance of the gelatinized (500 mg/kg) test lipid in sheep was 0.019 ± 0.002 corresponding to a half-time of 16.65 ± 1.74 minutes. With colloidal carbon (64 mg/kg), the phagocytic index in sheep was 0.080 ± 0.026, corresponding to a half-time of 6.16 ± 1.99 minutes. The per cent of injected lipid emulsion (%ID) in major RE organs, on a total organ basis (TO), was: liver = 15.69 ± 1.65%; spleen = 2.09 ± 0.78%. Localization in the lung = 31.39 ± 6.2%. The per cent of carbon localized in major RE organs (%ID/TO) was: liver = 21.37 ± 1.9%; spleen = 1.95 ± 0.55%. Localization in the lung = 32.70 ± 4.55%. In contrast, clearance and organ distribution of the blood-borne test microparticles in rats and dogs at the same relative challenging dose revealed a much more intense and rapid liver and spleen RES uptake with minimal lung localization (1-2%). Immunoreactive opsonic protein concentrations varied greatly with species and directly correlated with efficiency of RES function. Levels observed were: dog = 1285 ± 135 µg/ml; mouse = 1077 ± 67 µg/ml; rat = 400 ± 31 µg/ml; human = 297 ± 10 µg/ml; and sheep = 184 ± 13 µg/ml. After intravenous particulate challenge, circulating immunoreactive opsonic protein in the sheep was depleted (p < 0.05) rapidly with partial recovery at 24 hours and mild rebound hyperopsonemia at 48 hours. This pattern is in contrast to the rapid restoration seen in dog and rat within three to six hours postchallenge. Thus, in sheep, the extensive pulmonary localization of blood-borne microparticles appears related to inefficient RES clearance function mediated by a relative deficiency of circulating opsonic protein (plasma fibronectin).     

Reticulo-endothelial function in obstructive jaundice

A study of reticulo-endothelial function was performed in 30 patients with obstructive jaundice. Reticulo-endothelial phagocytic function, measured by the clearance of intravenous human micro-aggregated albumin, was significantly depressed in jaundiced patients compared with non-jaundiced controls (P less than 0.001). There was a significant correlation (P less than 0.001) between phagocytic function and plasma bilirubin level but not with transaminase or bile salt level. Phagocytic function was not related to the presence of malignancy, but was markedly reduced in patients with cholangitis. There was no reduction in hepatic sinusoidal blood flow, opsonin levels (fibronectin, IgG, complement) or serum opsonic activity to account for the reticulo-endothelial dysfunction.     

The effects of splenectomy and splenic implantation on alveolar macrophage function

The effect of splenectomy on the ability of alveolar macrophages of young and adult rats to phagocytize Pneumococci, Types 3 and 14, and Pseudomonas aeruginosa was studied. Young animals showed a significant (15%) decrease in the phagocytosis of pneumococci type 14, 4 weeks after splenectomy. This depression increased to 30% in 6 weeks' time. Such depression was also noted when young splenectomized rat alveolar macrophages were challenged with Pseudomonas aeruginosa but not with type 3 pneumococci 6 weeks postsplenectomy. Three months following splenectomy in young animals, the rats were grown and they seemed to regain their normal phagocytic activity against pneumococci type 14. Adult rats also showed no alteration in their phagocytic activity against type 3 pneumococci. Autoimplantation of the spleen had a protective effect on the phagocytosis of type 14 pneumococci, and a nonsignificant effect on that of type 3. The present study postulates a modulatory role of the spleen on alveolar macrophage function. Splenectomy may cause the impairment of local lower respiratory immune function, making lungs vulnerable to specific bacterial invasion. Such splenic modulatory effect on alveolar macrophage phagocytic function seems to be age and antigen specific.     

Measurements of reticuloendothelial system phagocytic activity in the rat after treatment with silica, liposomes, and cyclosporine

Reticuloendothelial system phagocytosis was evaluated in vivo by the clearance and tissue distribution of 99mTc-albumin millimicrospheres in rats. Administration of i.p. silica 2 days prior to clearance measurement increased the half-life of millimicrospheres 24% compared with control animals (P less than 0.01). Impairment of phagocytic activity was maintained at 5 days to 22% over control values (P less than 0.01). Tissue distribution studies showed that liver uptake was reduced and splenic and pulmonary uptake was increased compared with control. Cyclosporine i.v. increased half-life by 14% 1 hr after administration )P = NS) and half-life returned to control values by 8 hr. Hepatosplenic shift was less marked than after silica treatment. Phospholipid liposomes i.v. produced prompt impairment of millimicrosphere clearance after 1 hr; half-life was prolonged 46% over control values (P less than 0.001 vs. control) and marked radiolabel shift to the spleen and lung was seen. Measurements done 18 hr after a dose of liposomes revealed an increase of 55% over control half-life (P less than 0.001). Liposomes appear to be potent, nontoxic--and, in some cases, reversible agents--for blockade of reticuloendothelial phagocytosis and examination of non-phagocytic reticuloendothelial functions. These results help to explain some of the results obtained in pancreatic islet grafting and suggest that phospholipid liposomes may be useful in this form of transplantation.     

Effect of premedicants,intravenous anaesthetic agents and local anaesthetics on phagocytosis in vitro

Intact leucocyte function is essential for the body’s defense against infection. Any depression of leucocyte migration, phagocytosis and ability to kill invading organisms is likely to enhance morbidity and mortality from infection in the postoperative period. Although volatile anaesthetic agents have been shown to influence the leucocyte function adversely, yet the effects of non-volatile anaesthetic agents and other allied drugs on the leucocyte phagocytic activity have not been explored. Therefore, the effects of premedicants (morphine, meperidine, diazepam), intravenous induction agents (thiopentone, methohexitone, alfathesin, and ketamine), local anaesthetic agents (lidocaine, procaine, and bupivacaine), muscle relaxants (succinylcholine and tubocurarine), and other drugs (prednisolone, furosemide, aspirin, epinephrine and chlorpromazine), on the phagocytic activity of leucocytes was investigated in vitro. Leucocytes were separated from the blood samples taken from healthy human volunteers, treated with 10^–2 to 10^–6 molar concentrations of the drug under investigation and subsequently incubated at 37°C along with heat inactivated staphylococcus aureus to allow phagocytosis. Following incubation for one hour, cell smears were prepared and stained with haematoxylin. The number of bacteria ingested by one hundred leucocytes on the control and the drug treated cell smears were counted. The difference in phagocytosis between the control and the test cells when examined by analysis of variance revealed a statistically significant dose dependent inhibition of phagocytic activity under the influence of premedicants, intravenous induction agents, local anaesthetic agents (except bupivacaine), diazepam and chlorpromazine (P < 0.005). In contrast, muscle relaxants and other drugs failed to inhibit the leucocyte phagocytic activity in vitro. These observations indicate that different anaesthetic agents can adversely effect the leucocyte function in vitro; however, the mechanisms by which these agents produce a depression of phagocytosis are not clear at present.     

Experimental and clinical studies on the effect of reticuloendothelial system (RES) potentiator in the depressed RES function in cirrhotics

Among the patients with liver cirrhosis (LC) who undergo the operation, the postoperative complications are not infrequent and sometimes prove fatal. The impaired hepatic function, especially the impaired reticuloendothelial system (RES) function, has been claimed to be a possible pathogenic factor for these complications. The present experimental and clinical studies were undertaken to investigate the RES function and the effect of preoperative OK-432 administration as an RES potentiator in LC. The results are as follows: 1) CCl4-induced LC rats were evaluated for RES global phagocytic function, Kupffer cell phagocytic function, plasma opsonic activity and plasma opsonic substances such as fibronectin, C3 and IgG. All parameters except IgG showed significant depression compared to those values in normal rats. However, the administration of OK-432 (0.1 KE/rat, ip) improved all these depressed parameters. The OK-432 administration also significantly improved the survival following panperitonitis in LC rats. 2) Among 18 LC patients with hepatocellular carcinoma undergoing partial hepatectomy, the RES global phagocytic function, plasma opsonic activity and plasma opsonic substances were evaluated. Same as the experimental study, all parameters except IgG were significantly depressed among the LC patients compared to those values in the patients with normal liver. However, the preoperative OK-432 administration (5 KE/day sc for 4 days) significantly improved these parameters and consequently decreased the postoperative complications. These results indicate that the preoperative RES activation by the OK-432 was effective and useful for the prevention of the postoperative complications in the LC patients.     

Humoral and cellular changes of non-specific immune response following severe trauma

The influence of trauma and hemorrhagic shock on the non-specific immune system has been pointed out in various experimental studies. Other investigations have also been able to find a relationship between these changes and a higher incidence of post-traumatic complications in the form of organ failure. Our aim was to demonstrate the potential changes in the cellular defense system in a clinical study on multiple trauma patients. The polymorphonuclear leukocytes (PMNL) are the main representative of the mobile, non-specific immune system. Our study revealed a significant deterioration of PMNL function after trauma. The metabolic activity and phagocytic function were mainly affected by a decrease in the concentration of so-called "opsonins." The opsonins are important for the identification and engulfment of debris (necrosis, fat emboli and thrombi) and bacterial substances (endotoxin). Next to the opsonin level, a change in the receptor configuration is important for phagocytosis. However, we could not find any substantial evidence of surface receptor alteration. The reticuloendothelial cells (RES), a stationary phagocytic system, also showed a significant reduction in clearance function in these polytraumatized patients. Similar to PMNL, these disturbances were based on the reduction of the opsonine concentration. We were able to demonstrate a significant disturbance in immune function in multiple trauma patients with post-traumatic complications compared to patients with a normal clinical course after injury. Disturbances in the PMNL function (seen after 4 days) were found to appear after the RES disturbances. Systemic interaction between these two phagocytic systems cannot be excluded and further investigation is therefore required.     

The effect of preoperative corticosteroids on peritoneal macrophage function after laparoscopic and open abdominal surgery in a rat model

Background

Peritoneal macrophages play an important role in the immune response after abdominal operations. The stress response after these operations has been associated with impaired phagocytosis by peritoneal macrophages. This study examined the influence of minimally invasive techniques and preoperative corticosteroid administration on postoperative peritoneal macrophage phagocytic activity.

Methods

After IACUC approval, 66 Sprague Dawley rats were randomly divided into 7 groups: baseline animals (B), anesthesia controls (AC), open cecectomy (OC), and laparoscopic cecectomy (LC). Within the AC, OC, and LC groups, half received intraperitoneal (IP) dexamethasone (10 mg/kg) 1 hour before surgery (+S), and the other half received an equal volume of normal saline IP (−S). Animals were observed postoperatively for 24 hours and were then euthanized. Peritoneal macrophages were harvested via intraperitoneal lavage. A phagocytosis assay was performed to calculate the net phagocytosis and percent response to the effector agent. Statistical analysis was performed using analysis of variance and a Student t test between groups. A P value of <.05 was considered significant.

Results

Significant differences were observed between groups. The B group had a response rate of 94.2% ± 56.7%, which was not different from the AC groups (−S, P = .28; +S, P = .16) or the LC-S group (P = .9). The lowest phagocytic activity rate was in the OC-S group with a response rate of 33.8% ± 28.5%. The highest phagocytic response rates occurred in the AC +S (145.2% ± 60.2%) and LC +S (198.1% ± 103.5%). These were not significantly different from each other (P = .3). The LC +S group had a significantly higher percent response than all of the other groups. The phagocytic response rate of the OC +S group was not different from either the AC-S group (P = .07) or the LC-S group (P = .8); however, it was less than the AC +S group (P = .02) and the LC +S group (P = .003).

Conclusion

Open cecectomy resulted in greater impairment of the phagocytic activity of peritoneal macrophages than laparoscopic cecectomy. The addition of preoperative corticosteroids improved phagocytic activity back to baseline function. The combination of minimally invasive surgical technique and preoperative corticosteroid administration resulted in the greatest postoperative phagocytic function of peritoneal macrophages in a rat model.     

Biliary obstruction reduces hepatic killing and phagocytic clearance of circulating microorganisms in rats

Septic complications are common in patients with biliary obstruction. This is thought to be related, in part, to dysfunction of the hepatic reticuloendothelial system (RES). It has been reported that nearly 80% of circulating microorganisms are phagocytosed and killed within the liver and that clearance of circulating pathogens is significantly impaired in patients with jaundice. However, the effect of biliary obstruction specifically on phagocytic killing within the liver is less well described. Therefore this study was designed to quantify the effect of biliary obstruction, simultaneously and discriminately, on two important components of hepatic RES function (phagocytosis and phagocytic killing). Rats were divided into three experimental groups: control, sham, and jaundiced (common bile duct ligation). At 7, 10, 14, and 21days after operation, E. coli labeled with both ¹²⁵I and ⁵¹Cr were injected intravenously. Using the previously validated double-labeled in vivo E. coli technique, hepatic phagocytic clearance (HPC), hepatic killing efficiency (HKE), and net hepatic killing (NHK) were measured. Common bile duct ligation resulted in a significant decrease in the HPC of E. coli 10, 14, and 21days postoperatively. Similarly, HKE was significantly decreased in jaundiced animals by postoperative day 10, but returned to baseline values by day 14. The net effect of these changes in HPC and HKE values were reflected in a significant reduction in NHK in jaundiced animals. Results of the present study suggest that obstructive jaundice impairs both phagocytosis and phagocytic killing within the liver. These findings may help to explain the susceptibility of patients with biliary tract obstruction to the morbidity and mortality of septic complications. Presented at the Forty-Third Annual Meeting of The Society for Surgery of the Alimentary Tract, San Francisco, California, May 19–22, 2002 (poster presentation).     

Plasma fibronectin concentration in animal models of sepsis and endotoxemia

Plasma fibronectin is a nonspecific opsonin which mediates phagocytosis of particulate matter by macrophages. Fibronectin depletion results in depression of reticuloendothelial system phagocytic function. This may potentiate microvascular embolization and sludging in critical illness. It has been hypothesized that sepsis is a major cause of fibronectin depletion. To explore this hypothesis, plasma fibronectin concentrations were measured in rats with intraabdominal abscesses and in rabbits subjected to the generalized Shwartzman reaction (spaced doses of endotoxin). In both groups of animals there was a significant increase (P < 0.05) rather than decrease in fibronectin concentrations at times when sepsis and disseminated intravascular coagulation were manifest. This study does not support the hypothesized relationship between sepsis and fibronectin depletion. Until the kinetics of fibronectin production and utilization are further delineated, caution must be exercised in the interpretation of immunoreactive plasma fibronectin levels.     

Phagocytic function of polymorphonuclear leukocytes and the RES in endotoxemia

The reticuloendothelial system (RES) and the polymorphonuclear leukocytes (PMNs) are thought to play a major role in defense against sepsis. Disturbances in the function of these two phagocytic systems during a septic event is associated with the development of lung capillary injury. Endotoxemia is said to lead to similar changes. Our study examined the function of the RES and PMNs after bolus injection of endotoxin (2 micrograms/kg BW) in a standardized sheep model. For up to 24 hr after endotoxin, blood samples were drawn and PMN function was followed by chemiluminescence, chemotaxis, and adherence as well as the phagocytosis and killing of bacteria. RES function was determined by the blood clearance of a labeled Tc99 colloid. We found an increase of RES clearance directly after endotoxin. Chemotaxis, phagocytosis, and killing were reduced. Adherence was increased. Chemiluminescence peak maximum (CLPM), representing the metabolic activity of the PMNs, was initially increased but shortly thereafter showed a significant decline (at 1 hr: 0.52 +/- 0.13 X 10(6) cpm with P less than 0.05 compared to baseline). The chemiluminescence peak time (CLPT), a measure of membrane receptor function, was significantly reduced (10.0 +/- 2.2 min with P less than 0.001 compared to baseline). Endotoxin led to a reduction of intracellular PMN functions (phagocytosis, killing, CLPM) within 1 hr. Membrane localized functions (adherence, CLPT) were increased. The changes in PMN function might be the reason for the development of lung capillary injury, in spite of undisturbed RES clearance.     

Phagocytosis by emigrated,intra-abdominal neutrophils is depressed during human secondary peritonitis

The phagocytic function of neutrophils is a crucial element in host defense against invading microorganisms. Patients with diffuse peritonitis depend on adequate reactivity of neutrophils, in particular locally in the peritoneal cavity as well as in the circulation. This study examined phagocytosis as well as numerical expression of Fcgamma I-III (CD16, CD32, CD64) and complement receptors (CD18, CD35) of emigrated, intra-abdominal and circulating neutrophils during human secondary peritonitis using fluorescence-activated cell analysis. Optimally opsonized E. coli bacteria were used independently of the well-known low level of opsonic molecules during peritonitis. Compared with controls (abdominal surgery without peritonitis), the percentage of emigrated neutrophils which engulfed E. coli bacteria was significantly depressed until 48 h after diagnosis of, and surgery for, peritonitis. When patients with complicated peritonitis (septic shock, multiple organ failure) were compared with patients without complications, phagocytosis was even more depressed in patients with complications. Numerical expression of CD64 (Fcgamma RI) and CD35 (CR1) increased significantly on emigrated polymorphonuclear leukocytes (PMNs) during peritonitis when compared to controls. There was no difference in CD18 and CD32 (Fcgamma RII) expression between the two groups. Numerical expression of CD16 (Fcgamma RIII) on emigrated PMNs decreased significantly in peritonitis. This was more pronounced in patients with complicated peritonitis. We conclude that there is a long-lasting depression of phagocytosis by emigrated PMNs during peritonitis, independent of the opsonic activity. Our data suggest that decreased phagocytosis might be correlated to the profound drop in CD16 on these cells.