Laparoscopic versus conventional Nissen fundoplication: the influence on plasma insulin-like growth factor-I and insulin-like growth factor binding protein-3

BACKGROUND

Conventional surgery is known to influence postoperative insulin-like growth factor-I (IGF-I) levels and to increase protein breakdown. Recent animal data described that laparoscopic surgery, in contrast to conventional surgery, maintains postoperative IGF-I levels, suggesting a reduced postoperative catabolic response.

AIM

The aim of this study was to demonstrate differences in the postoperative catabolic response between laparoscopic and conventional surgery.

METHODS

Seventeen patients scheduled for Nissen fundoplication were randomly assigned to undergo either a laparoscopic or a conventional procedure. The catabolic response was assessed by measuring total IGF-I and insulin-like growth factor binding protein-3 (IGFBP-3).

RESULTS

IGF-I levels decreased significantly 4 days after both types of surgery. IGFBP-3 decreased more rapidly after conventional surgery than after the laparoscopic technique; however, the differences between the groups were not significant.

CONCLUSION

In contrast to animal data, no differences in plasma IGF-I or IGFBP-3 were seen in patients undergoing laparoscopic or conventional Nissen fundoplication.

Accumulation of omental mast cells during peritoneal dialysis

OBJECTIVE

New vessel formation has been reported in various tissues during peritoneal dialysis (PD). In that line, mast cells can produce factors such as tryptase, chymase, or basic fibroblast growth factor that might contribute to the formation of new vessels. In the present study, the association of mast cells with neovascularization during PD was investigated.

METHODS

Rats received daily 10 mL infusions of conventional 3.86% glucose-containing PD fluid over a 10-week period. The infusions were delivered through a subcutaneously implanted mini access port that was connected by catheter to the peritoneal cavity. Untreated rats served as a control group. The number of blood vessels and of mast cells in the omentum were counted. Also, the number of peritoneal mast cells was determined.

RESULTS

Chronic exposure to PD fluid resulted in an increased number of mast cells in the omentum. However, no clear correlation was found between the elevated number of omental blood vessels and the number of mast cells in the omentum or in the peritoneal cavity.

CONCLUSIONS

Omental mast cells accumulated dramatically upon exposure to PD fluid. The actual role of accumulated omental mast cells in the induction of angiogenesis during PD should, however, be further investigated.

Analysis of monocyte chemotactic protein-1 production in different major histocompatability complex-restricted antigen presentation systems

In the present study the production of the CC chemokine monocyte chemotactic protein-1 (MCP-1) in several MHC II-restricted antigen presentation systems was investigated in vitro. To assess which type of antigen-presenting cell (APC) influences MCP-1 production during antigen presentation, cultures enriched for different APC populations were prepared and MCP-1 production was determined. Our results showed that APCs that effectively induce a T cell response also produce elevated amounts of MCP-1. The MCP-1 production is highest in the memory-driven secondary response against a single antigen. Despite a massive T cell proliferation, low MCP-1 concentrations are found in Con A-induced cultures. These results suggest that T cell proliferation alone is not sufficient for MCP-1 production and that stimulation of the APC during the process of antigen presentation results in MCP-1 production. Based on our results and the literature, we propose a model for MCP-1 as an enhancer of the adaptive immune response.

Immune-stimulating effects of low-dose perioperative recombinant granulocyte-macrophage colony-stimulating factor in patients operated on for primary colorectal carcinoma

BACKGROUND

Surgery induces a postoperative immunosuppression, thereby possibly facilitating the outgrowth of pre-existing occult metastases or the seeding of disseminated tumour cells in patients with primary colorectal carcinoma operated on with curative intent. The hypothesis that adjuvant therapy with perioperative recombinant human granulocyte-macrophage colony-stimulating factor (rhGM-CSF) would minimize postoperative immunosuppression was investigated in this pilot study.

METHODS

Patients were allocated randomly to receive daily subcutaneous injections with either saline (n = 8) or rhGM-CSF 2.8 microg per kg body-weight (n = 8) from 3 days before operation until 4 days afterwards. Phytohaemagglutinin (PHA) skin test reactivity, monocyte human leucocyte antigen (HLA) DR expression and the extent of the acute-phase response, by determination of white blood cell count and differentiation, plasma interleukin (IL) 6 levels and body temperature in the perioperative period, were examined.

RESULTS

rhGM-CSF treatment minimized postoperative suppression in PHA skin test reactivity and increased the numbers of neutrophils and monocytes while enhancing the expression of HLA-DR in the postoperative period. Additionally, both postoperative plasma IL-6 levels and the incidence of fever tended to be higher in the rhGM-CSF group.

CONCLUSION

In this pilot study, perioperative administration of low-dose rhGM-CSF stimulated certain immune functions that are normally depressed after operation. The implications for the antitumour responses directly after operation and the formation of liver metastases are currently under investigation.

Rat models in peritoneal dialysis

BACKGROUND

It is widely accepted that the currently used dialysis solutions are not biocompatible with the peritoneal membrane. Therefore, animal studies have been performed to study different aspects of peritoneal dialysis. However, representative models mimicking the human situation are not yet available.

METHODS

The effect of a single injection of peritoneal dialysis (PD) fluid on the cellular composition was studied. Thereafter, the effect of a single injection of PD fluid on bacterial clearing was tested over time. Finally, an in vivo rat model was established to study the effects of long-term exposure to PD fluid on the peritoneal membrane and the local host defence (peritoneal cells).

RESULTS

In the rat model, long-term daily exposure is possible. The 'drop-out' after 9-10 weeks on the most commonly used PD fluid Dianeal 3.86%, however, is approximately 50% due to omental wrapping. In the remaining study group, large differences were observed (as compared with controls), especially with respect to morphological parameters.

CONCLUSIONS

The rat peritoneal continuous exposure model seems to have potential for intervention studies, since it uses no additions, no antibiotics and no omentomectomy, and gives continuous long-term exposure to PD fluid. However, problems still remain: 'drop-out' is quite often seen and this non-uraemic exposure model does not totally mimic the situation present in continuous ambulatory PD patients.

Effect of PD fluid instillation on the peritonitis-induced influx and bacterial clearing capacity of peritoneal cells

BACKGROUND

The commonly used peritoneal dialysis fluids contain glucose as the osmotic agent. Heat sterilization leads to the formation of glucose degradation products which contribute, together with glucose, to the formation of advanced glycation end-products (AGEs). AGEs have been shown to be present in the peritoneal cavity. Methods have been developed to minimize the amount of glucose degradation products in peritoneal dialysis fluids. In a rat peritoneal dialysis model, we compare the effect of a commonly used peritoneal dialysis fluid, Gambrosol, with a newly developed peritoneal dialysis fluid, PD-Bio, on the influx and functional capacity of the peritoneal cells after 2 weeks of peritoneal dialysis fluid instillation.

METHODS

Three groups of animals were used: rats received daily infusion with 15 ml of either 4% Gambrosol (group 1) or 4% PD-Bio (group 2), and a control group of animals did not receive fluid (group 3). After 2 weeks of PD fluid instillation, all the animals were injected with a 0.5 ml suspension containing 3x10(8) colony-forming units of Staphylococcus aureus. The in vivo bacterial clearing capacity was determined after 15 h.

RESULTS

A statistically significant higher leukocyte influx was found in the control group compared with both PD fluid-injected groups. No statistical differences in bacterial clearing were observed among the three groups, although the number of bacteria recovered from the PD-Bio group tended to be lower than that from the Gambrosol group. Moreover, in both PD fluid instillation groups, the bacteria tended to be cleared more slowly compared with the control group. The number of mesothelial cells in the PD fluid groups was significantly greater than in the control group.

CONCLUSION

No differences were observed in bacterial clearing capacity, leukocyte influx and mesothelial cell number after a 2 week exposure of the peritoneal cavity to Gambrosol vs PD-Bio.

The influence of laparoscopic surgery on postoperative polymorphonuclear leukocyte function

BACKGROUND

Laparoscopic surgery is thought to result in a better preservation of patients' immunological defenses. Polymorphonuclear leukocytes (PMN) are the most important effector cells in the elimination of pathogenic microorganisms. Because little is known about their function after laparoscopic surgery, we studied PMN phagocytosis, antigen expression, and oxygen radical production.

METHODS

In this study, 17 patients scheduled for Nissen fundoplication were randomly assigned to undergo either a laparoscopic or conventional procedure. To study phagocytic capacity, PMN were incubated with fluorescein isothiocyanate (FITC)-labeled Staphylococcus aureus. Plasma opsonic capacity was measured by comparing PMN phagocytosis in the presence of patients' own plasma with phagocytosis in the presence of control plasma. Cellular activation was measured by the expression of various cell surface markers and by assessment of PMA-stimulated oxidative burst.

RESULTS

Phagocytosis by PMN in the presence of patients' plasma was significantly lower 2 h after the conventional operation. No decrease in phagocytosis was observed when control plasma was used, indicating a decreased opsonic capacity of plasma after conventional surgery. No changes were observed after laparoscopic surgery. Furthermore, CD11b expression was significantly lower after the laparoscopic approach, indicating a blunted cellular activation. A significantly lower PMA-stimulated oxidative burst further confirmed the tempered stimulation after laparoscopic surgery.

CONCLUSIONS

Laparoscopic surgery results in a preservation of the plasma opsonic capacity, and thereby the ability of PMN to phagocytose bacteria. Moreover, the postoperative cellular activation is reduced. The preserved phagocytosis and the blunted activation may prevent the development of postoperative infectious complications.

Bactericidal/permeability-increasing protein preserves leukocyte functions after major liver resection

OBJECTIVE

To analyze postoperative leukocyte functions in patients undergoing hemihepatectomy, and to assess the effect of treatment with the endotoxin-neutralizing agent bactericidal/permeability-increasing protein (rBPI21).

SUMMARY BACKGROUND DATA

Extensive liver resection is associated with a high incidence of infectious complications. Because elimination of pathogenic microorganisms occurs mainly by leukocytes, this increased rate of infections is most likely due to an impaired function of these cells. Endotoxin, translocated from the gut into the systemic circulation as a result of increased gut permeability and reduced hepatic clearance function after major liver resection, may play an important role in the impairment of posthepatectomy leukocyte function.

METHODS

To investigate whether hemihepatectomy results in impaired leukocyte functions and to determine the role of endotoxin in this process, leukocyte oxidative burst and leukocyte antigen expression were studied in three groups of patients: patients undergoing a hemihepatectomy and receiving rBPI21 treatment, patients undergoing hemihepatectomy and receiving placebo, and as an extra control group patients undergoing other major abdominal surgeries. Blood samples were collected before surgery, 2 hours after surgery, and at days 1, 2, 5, and 7. Phorbol myristate acetate-stimulated oxidative burst was measured using dihydrorhodamine, and leukocyte surface expression of the antigens CD11b, CD16, and CD14 was investigated by indirect immunofluorescence. Both oxidative burst and membrane surface expression were quantified by flow cytometry. An indication of the antiendotoxin effect of rBPI21 treatment was provided by assessment of plasma lipopolysaccharide binding protein (LBP) levels by enzyme-linked immunosorbent assay.

RESULTS

The oxidative burst in the hemihepatectomized patients receiving placebo and the controls increased 2 hours after surgery, whereas it decreased in the rBPI21-treated patients, resulting in significant differences between the groups. On day 1, neutrophil CD11b expression and monocyte CD14 expression in the rBPI21-treated patients and controls were significantly lower than in the placebo group. At 2 hours, CD16 expression in the placebo-treated patients was significantly higher than in the rBPI21-treated patients and controls. On day 5 and day 7, plasma LBP levels were significantly higher in the placebo-treated patients compared with the rBPI21-treated patients.

CONCLUSIONS

The results of this study show that patients undergoing major liver resection have an increased activation of leukocytes compared with those undergoing other major abdominal surgery. This enhanced activation may contribute to the increased risk of infection in these patients. Administration of the endotoxin-neutralizing agent rBPI21 to hemihepatectomy patients was shown to reduce plasma LBP levels, to preserve leukocyte functions partially, and to reduce leukocyte activation to the level of other, nonhepatic abdominal surgery.

The degree of branching of the glycans of alpha(1)-acid glycoprotein in asthma. A correlation with lung function and inflammatory parameters

Alpha(1)-acid glycoprotein (AGP) is a plasma protein belonging to the group of acute-phase proteins. It contains five N-linked glycans which, depending on pathophysiologic state, differ in their degree of branching (i.e., in the relative proportions of di-, tri-, and tetraantennary glycans). Changes in the degree of branching of these glycans have been shown to affect various immunomodulatory properties of AGP. We wanted to investigate whether changes occur in the branching of AGP glycans in plasma and in bronchoalveolar lavage fluid (BALF) in asthma. For this purpose, we selected three groups of patients for study: patients with atopic asthma (AA), atopic nonasthmatic patients, and a group of patients with various interstitial lung diseases (ILDs). The plasma AGP concentration was normal in both atopic study groups, but was increased in ILD patients. In contrast, the branching of glycans of AGP was altered in subjects with AA, whereas it was normal in the other study groups. The presence of asthma symptoms correlated with the increased glycan branching of AGP in both plasma and BALF. Additionally, the degree of branching of AGP in BALF was related to FEV(1), to the provocative dose of histamine causing a 20% decrease in FEV (PD(20)), and to the number of eosinophils. In conclusion, asthma is accompanied by changes in the branching of AGP glycans that indicate an inflammatory reaction that differs markedly from a normal acute-phase response, in which decreased branching of AGP occurs.

Laparoscopic surgery preserves monocyte-mediated tumor cell killing in contrast to the conventional approach

BACKGROUND

Experimental animal research shows that immunologic defenses against tumor cells are disturbed by surgical trauma, resulting in an increased rate of tumor implantation and the growth of subsequent metastases. Minimally invasive surgery is associated with a preservation of postoperative immunologic functions and, in animal models, with decreased tumor growth. The objective was to study the influence of several surgical procedures, approached conventionally and laparoscopically, on interleukin-6 (IL-6) and monocyte-mediated cytotoxicity (MMC).

METHODS

Five groups of five patients each were included in this prospective study: laparoscopic cholecystectomy (minor trauma) group, Nissen fundoplication (laparoscopic and conventional as moderate trauma) groups, and sigmoid colectomy (laparoscopic and conventional as major trauma) groups. Preoperatively, 1 and 4 days after surgery, IL-6 and MMC against SW948 colon cancer cell line were determined.

RESULTS

The IL-6 levels differed significantly between the three laparoscopic procedures (p = 0.004) and increased according to the degree of trauma. There was no significant difference in MMC between the three laparoscopic procedures. However, MMC was suppressed after conventional procedures and preserved after laparoscopic procedures (p = 0.001). There was no correlation between IL-6 levels and changes in MMC.

CONCLUSIONS

More extensive laparoscopic procedures induce increased levels of IL-6, reflecting higher levels of trauma. Conventional surgical procedures result in depressed MMC in the postoperative period. After laparoscopic procedures, MMC is preserved. These findings may be of importance in preventing implantation and growth of cancer cells spread by surgical manipulation.

Regulation of CD 163 on human macrophages: cross-linking of CD163 induces signaling and activation

CD163 is a member of the group B scavenger receptor cysteine-rich (SRCR) superfamily. This study describes aspects of the tissue distribution, the regulation of expression, and signal transduction after cross-linking of this receptor at the cell surface of macrophages. CD163 showed an exclusive expression on resident macrophages (e.g., red pulp macrophages, alveolar macrophages). The expression was inducible on monocyte-derived macrophages by glucocorticoids but not by interleukin-4 (IL-4), granulocyte-macrophage colony-stimulating factor (GM-CSF), and interferon-gamma. The combination of IL-4 or GM-CSF with glucocorticoids resulted in a further increase. Subcellular analysis of alveolar macrophages by immunoelectron microscopy showed a plasma membrane localization of the antigen. Cross-linking of CD163 with monoclonal antibody induced a protein tyrosine kinase-dependent signal that resulted in (1) slow-type calcium mobilization, (2) inositol triphosphate production, and (3) secretion of IL-6 and GM-CSF. The data suggest a function for the SRCR-superfamily receptor CD163 in the regulation of inflammatory processes by macrophages.

Infection of human endothelial cells with Staphylococcus aureus induces the production of monocyte chemotactic protein-1 (MCP-1) and monocyte chemotaxis

Bacterial infection coincides with migration of leucocytes from the circulation into the bacterium-infected tissue. Recently, we have shown that endothelial cells, upon binding and ingestion of Staphylococcus aureus, exhibit proinflammatory properties including procoagulant activity and increased intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) expression on the cell surface, resulting in hyperadhesiveness, mainly for monocytes. The enhanced extravasation of monocytes to bacterium-infected sites is facilitated by the local production of chemotactic factors. From another study we concluded that the locally produced chemokine MCP-1 is important in the recruitment of monocytes to the peritoneal cavity in a model of bacterial peritonitis. In the present study we investigated whether cultured human endothelial cells after infection with bacteria produce and release MCP-1, which in turn stimulates monocyte chemotaxis. We observed that endothelial cells released significant amounts of MCP-1 within 48 h after ingestion of S. aureus. This was dependent on the number and the virulence of the bacteria used to infect the endothelial cells. The kinetics as well as the amount of MCP-1 released by S. aureus-infected endothelial cells differed markedly from that released by endothelial cells upon stimulation with IL-1beta. Supernatant from S. aureus-infected or IL-1beta-stimulated cells promoted monocyte chemotaxis which was almost entirely abrogated in the presence of neutralizing anti-MCP-1 antibody, indicating that most of the chemotactic activity was due to the release of MCP-1 into the supernatant. Our findings support the notion that endothelial cells can actively initiate and sustain an inflammatory response after an encounter with pathogenic microorganisms, without the intervention of macrophage-derived proinflammatory cytokines.

A prospective randomized study of the systemic immune response after laparoscopic and conventional Nissen fundoplication

BACKGROUND

Laparoscopic techniques are thought to reduce the postoperative immunologic and metabolic changes of conventional operations. Until now, the only clinical data available were obtained from patients operated on for symptomatic gallstones; moreover, few studies were randomized. This randomized prospective study compares the systemic immune response after laparoscopic and conventional Nissen fundoplication.

METHODS

Seventeen patients scheduled for Nissen fundoplication were randomly assigned to undergo either a laparoscopic or a conventional procedure. Postoperative inflammatory response was assessed by measuring the white blood cell count, C-reactive protein, and soluble tumor necrosis factor receptors p55 and p75. Postoperative immune function was assessed by measuring monocyte HLA-DR expression and the stress response was assessed by measuring plasma cortisol concentrations.

RESULTS

Laparoscopic surgery resulted in significantly lower plasma CRP levels 1 day after surgery. Both approaches resulted in a significant decrease in HLA-DR expression within 2 hours after surgery. After the laparoscopic approach, postoperative expression was restored to preoperative values within 1 day after surgery. However, after conventional surgery HLA-DR expression remained suppressed and did not return to preoperative values until the fourth postoperative day. No significant differences between the 2 procedures were observed in white cell blood count, sTNFr-p55 and p75, nor in postoperative cortisol levels.

CONCLUSIONS

Although both laparoscopic and conventional Nissen fundoplication result in an activation of the systemic immune response, this study suggests that this response could be less after the laparoscopic approach. The differences found may reflect a lower risk for postoperative infective complications.

Immunological consequences of laparoscopic surgery, speculations on the cause and clinical implications

BACKGROUND

Immune suppression is an established consequence of surgical stress and trauma. Postoperative changes in the systemic immune system are proportional to the degree of surgical trauma and subsequent immune suppression may be implicated in the development of infectious complications and tumor metastasis formation. Laparoscopic surgery reduces the magnitude of the operative trauma and is thought to preserve postoperative immunological defenses.

METHODS

Relevant literature concerning postoperative immune functions and laparoscopic surgery was reviewed and clinical implications are discussed.

RESULTS

The influence of laparoscopic surgery on the postoperative systemic immune response is significantly less after laparoscopic cholecystectomy than with the conventional approach. Few immunological data are available concerning more advanced laparoscopic procedures. Various animal model studies of postoperative septic complications and tumor growth show that the postoperative preservation of the systemic immune response after laparoscopic surgery can have enormous clinical advantages.

CONCLUSION

Laparoscopic surgery preserves the postoperative immunological defenses. In the future, this may imply a lower number of infections, less local recurrence and even fewer distant metastases. Prospective randomized studies are necessary to see whether these suspected advantages can be demonstrated in clinical practice.

Impaired leukocyte phagocytosis in patients undergoing hemihepatectomy for liver metastases

Patients undergoing partial hepatectomy have an increased susceptibility to infection. To investigate whether this increased risk is related to impaired leukocyte function, we studied polymorphonuclear leukocyte (PMN) phagocytosis in patients undergoing a hemihepatectomy because of liver metastasis (LM, n = 11) and in patients undergoing major abdominal surgery because of abdominal malignancy (AM, n = 8). Eight healthy volunteers (HVs) served as controls. Leukocyte suspensions were incubated with fluorescein isothiocyanate-labeled Staphylococcus aureus, and phagocytosis was measured by flow cytometry. Preoperative PMN phagocytosis, in the presence of autologous plasma, was significantly less in patients with LM compared with patients with AM or HVs. This impaired phagocytosis was potentially restored in the presence of normal plasma. The decreased phagocytic capacity of PMNs from patients with LM was not related to levels of known plasma opsonins or phenotypic changes of PMNs. Rather, it was related to a deficiency of unidentified plasma factors. After surgery, the phagocytic capacity of PMNs of patients with AM decreased by approximately 30%, which correlated with decreasing levels of immunoglobulin G and C3. In conclusion, patients with LM had a decreased PMN phagocytic capacity before surgery. This impairment in phagocytosis disappeared 1 week after surgery. We propose that the presence of LM leads to a deficiency of factor(s) in the blood that impairs PMN phagocytic capacity.

Glucocorticoids modulate the development of dendritic cells from blood precursors

Dendritic cells (DC) are professional antigen-presenting cells, capable of priming naive T cell responses. Glucocorticoids (GC) are frequently used in asthmatic patients. In this study we describe the effects of GC on the development and function of monocyte-derived DC (MoDC) in vitro and in vivo. Monocytes from healthy individuals were isolated and incubated with granulocyte-macrophage colony-stimulating factor (GM-CSF) and IL-4 for 6 days, to induce maturation into MoDC. To study the role of GC on DC differentiation in vitro cells were incubated with dexamethasone at different stages of MoDC development. At day 6 cells were characterized phenotypically by flow cytometry and functionally in an allogeneic mixed leucocyte reaction. To study the effect of GC in vivo patients with mild/moderate atopic asthma were selected. In one group no GC were used, whereas the other group used inhalation GC. MoDC from these patients were generated as described above and tested functionally. Incubation of MoDC or its peripheral blood precursors with dexamethasone decreased the accessory potency dose-dependently. The functional differences could not be explained by the changes in the expression of MHC II and the costimulatory molecules CD40 and CD86. The relevance of this mechanism was confirmed for the in vivo situation as well. MoDC from patients using inhalation GC showed a decreased accessory potency. These data suggest a modulatory effect of GC therapy at the level of the peripheral blood monocyte. The results indicate that GC influence DC development and function in vitro as well as in vivo.

Expression of MCP-1 by reactive astrocytes in demyelinating multiple sclerosis lesions

The pathology of multiple sclerosis (MS) is characterized by breakdown of the blood-brain barrier (BBB), accompanied by infiltration of macrophages and T lymphocytes into the central nervous system (CNS). The migration of these cells into the CNS parenchyma may be partly regulated by chemokines. The aim of this study was therefore to investigate the cellular localization of the potent monocyte- and T-cell-attracting chemokine monocyte chemoattractant protein (MCP)-1 by immunohistochemistry on postmortem brain tissue from MS and normal control cases. Brain tissue samples of six MS patients and four patients without a history of brain disease were neuropathologically classified according to characteristic (immuno)histochemical staining patterns. Frozen tissue sections of active demyelinating MS lesions, chronic active demyelinating MS lesions, and normal control brain were immunohistochemically stained with a monoclonal antibody directed against MCP-1. In active demyelinating MS lesions as well as in chronic active MS lesions, reactive hypertrophic astrocytes were strongly immunoreactive for MCP-1, whereas perivascular and parenchymal foamy macrophages did not express MCP-1 protein. These results suggest a significant role for the beta-chemokine MCP-1, synthesized in vivo by reactive hypertrophic astrocytes, in the recruitment and activation of myelin-degrading macrophages and thereby contributing to the evolution of MS lesions.

Experimental models in peritoneal dialysis: a European experience

BACKGROUND

The development of adequate animal models is important for the in vivo study of selected aspects of peritoneal dialysis (PD) that cannot be evaluated by an in vitro model, such as peritoneal membrane transport, the influence of local defense mechanisms, and for testing new osmotic agents and their biocompatibilities.

METHODS

Our experience with animal models for PD, including the acute Stockholm model in non-uremic rats, the acute and chronic Amsterdam model in non-uremic rats, and the chronic Gent model in uremic rats, is described.

RESULTS

The Stockholm model proved to be useful in understanding the normal physiology of peritoneal transport, and for testing new dialysis solutions and their biocompatibilities. It is a rather simple and inexpensive model, and thus is suitable for screening new solutions and additives. The Amsterdam model permits the study of chemokines and mesothelial cell regeneration in vivo, and is applied in a model of chronic peritonitis. The results of the Gent model suggest that chronic peritoneal dialysis in uremic rats is feasible for at least eight weeks. This model is, however, very laborious, time consuming, and expensive.

CONCLUSION

Further improvement of the technique and increase of the dialysis dose should result in a better and more realistic model for peritoneal dialysis. It is hoped that in the future these models will be useful to test the effects of long-term intraperitoneal application of different dialysis solutions and additives in uremic animals.

Talc-induced inflammation in the pleural cavity

Talc administration into the pleural cavity induces pleurodesis. To obtain further insight into the inflammatory process that causes pleurodesis, the cellular kinetics in the pleural space after the administration of talc was studied, along with its relation to chemokine concentrations in the pleural fluid. Thirteen consecutive patients with idiopathic spontaneous pneumothorax and eight patients with malignant pleural effusions received talc pleurodesis. The first group was treated with talc poudrage, whereas the second group was treated with talc slurry. Pleural fluids were isolated before talc administration as well as 3, 6, 24, 48 and 72 h afterwards. The talc induced a rapid polymorphonuclear neutrophil (PMN) influx followed by an accumulation of macrophages. In addition, increased production of interleukin (IL)-8 and monocyte chemotactic protein (MCP)-1 was observed. The talc-induced PMN influx reached its maximum after 3-24 h, and was related to the IL-8 concentration. In contrast, the MCP-1 was not related to the macrophage accumulation. Talc-induced inflammation in patients with idiopathic spontaneous pneumothorax and malignant pleural effusion is characterized by an influx of polymorphonuclear neutrophils related to interleukin-8, followed by an accumulation of monocytes.

Chemokines produced by mesothelial cells: huGRO-alpha, IP-10, MCP-1 and RANTES

Recently we showed the in vivo relevance of chemokines in cases of bacterial peritonitis in continuous ambulatory peritoneal dialysis (CAPD) patients. Mesothelial cells, the most numerous cells in the peritoneal cavity, are hypothesized to function as a main source of chemokine production. We investigated the time- and dose-dependent expression patterns of four chemokines by mesothelial cells at the mRNA and protein level in response to stimulation with physiological doses of proinflammatory mediators that are present at the site of bacterial inflammation. Besides the chemokines huGRO-alpha (attractant for neutrophils), MCP-1 and RANTES (monocyte attractants), the expression and production of IP-10 was analysed. Mesothelial cells were cultured and stimulated with either IL-1beta, tumour necrosis factor-alpha (TNF-alpha) or IFN-gamma or combinations of these. The time- and dose-dependent mRNA expression of the chemokines was determined by Northern blot analysis and the protein production by ELISA. It was concluded that mesothelial cells could indeed be triggered by the mentioned stimuli to induce mRNA and protein production (huGRO-alpha and IP-10) or to augment constitutive protein production (MCP-1). However, RANTES mRNA and protein production could only be induced in some cases and only in small amounts. The chemokine response of mesothelial cells was regulated differentially, depending on the stimulus and the chemokine measured. In distinct cases, combination of the stimuli led to synergy in mRNA expression and protein production. The presented in vitro data support our hypothesis that mesothelial cells in vivo are the main source of relevant chemokines in response to proinflammatory mediators, suggesting an important role for mesothelial cells in host defence.

Ontogeny of milky spots in the human greater omentum: an immunochemical study

BACKGROUND

Milky spots in the human greater omentum are preformed specific accumulations of primarily macrophages within the stroma of the greater omentum. To obtain a better understanding of milky spots in the human greater omentum, the development and the earliest forms of milky spots in the human greater omentum were studied, with special attention to the macrophage population.

METHODS

Specimens of human greater omentum were obtained from fetuses of 20 to 40 weeks gestation and one newborn three days old (n = 6). Using mature macrophages (RFD 7), activated macrophages (RFD 1), B-lymphocytes (CD 22), and T-lymphocytes (CD 2), and immunoperoxydase labeling, the percentage of these cells in developing milky spots and the development of milky spots were studied by light microscopy. A time-dependent increase in the percentage of positive staining cells and the size of clusters was analyzed using the non-parametric Spearman rank correlation test.

RESULTS

Small accumulations of cells with about 50% monocytes/macrophages were present at 20 weeks of gestation. With increasing gestational age the number of clusters of cells increased significantly (P < 0.01) as well as their size (P < 0.01). Starting at 29 weeks, vascularized clusters of cells were seen; true milky spots were present at 35 weeks. A significant (P < 0.05) increase in the percentage of mature macrophages was found in developing milky spots, whereas no activated macrophages were seen. The percentage of B-lymphocytes and T-lymphocytes found in the clusters of cells and milky spots increased significantly (P < 0.05) but did not exceed 10% of the total number of cells.

CONCLUSIONS

From our data it can be concluded that milky spots are specific structures in the greater omentum formed between the 20th and 35th week of gestation. Further, we concluded that immature cells (promonocytes) mature locally in developing milky spots.

Effect of peritoneal dialysis fluid measured in vivo in a rat-model of continuous peritoneal dialysis

To study the long-term effects of dialysis fluids on the peritoneal cavity, an in vivo model for continuous peritoneal dialysis in rats was developed. Mini vascular access ports were implanted subcutaneously in the neck of the rats and an attached catheter was instilled into the peritoneal cavity. Rats were injected daily with 10 mL of standard 3.86% Dianeal or saline for a period up to 12 weeks. In the peritoneal cavity an initial increase in total cells was observed after 4 weeks of fluid instillation. This had declined after 12 weeks. A similar trend was also seen for macrophage and neutrophil numbers, whereas the percentage of lymphocytes kept increasing in time. An effect of fluid instillation was observed on the density and the morphology of the mesothelial monolayer of the rats. A higher density of cells was observed after 12 weeks, and foci of young mesothelial cells within activated mesothelium were found. The results show that the rat model presented can be compared with the situation in the peritoneal cavity of continuous ambulatory peritoneal dialysis (CAPD) patients, and therefore is suitable for intervention studies.

Functional and phenotypic differences of monocyte-derived dendritic cells from allergic and nonallergic patients

BACKGROUND

Several studies suggest a role for dendritic cell in the pathogenesis of allergic disease.

OBJECTIVE

The purpose of this study was to compare function and phenotype of monocyte-derived dendritic cells (MoDC) from allergic asthmatic patients and healthy control subjects.

METHODS

MoDCs were developed by incubating adherent monocytes for 5 days with IL-4 and granulocyte-macrophage colony-stimulating factor. Phenotype was assessed with flow cytometry, and the antigen-presenting function was assessed with the allogeneic mixed leukocyte reaction and an autologous specific antigen presentation.

RESULTS

The morphology of the MoDCs was characteristic for immature dendritic cells. MoDCs from allergic asthmatic patients showed phenotypic differences in the expression of HLA-DR, CD11b, and the high-affinity receptor for IgE. A clearly enhanced accessory potential of MoDCs from atopic asthmatic patients in the mixed leukocyte reaction was also shown. Moreover, house dust mite-specific T-cell proliferation was increased.

CONCLUSION

This study suggests the involvement of dendritic cells in the pathogenesis of atopic asthma by an increased immunostimulatory capacity of MoDCs.

Production of IL-1 beta and TNF-alpha by peritoneal macrophages depends on the bacterial species and the inoculum

Peritoneal macrophages (PMs) are very potent producers of proinflammatory stimuli, such as interleukin (IL)-1 beta and tumor necrosis factor (TNF)-alpha. After contact with invading micro-organisms, PMs produce different cytokines, both pro- and anti-inflammatory. Therefore, they are crucial in the regulation of inflammatory events. The aim of this study was to investigate whether the production of IL-1 beta and TNF-alpha is dependent on the bacterial species used. PMs were harvested from spent peritoneal dialysis effluent and subsequently stimulated with five strains of bacteria in two different concentrations. After 24 hours of stimulation, supernatants were harvested and analyzed for both IL-1 beta and TNF-alpha content. IL-1 beta was measured with a commercial ELISA, and TNF-alpha was determined with a bioassay. Both the IL-1 beta and the TNF-alpha production were species-dependent. One strain of Staphylococcus aureus and one strain of Staphylococcus epidermidis induced a markedly higher response in both IL-1 beta and TNF-alpha than the other species. This response was also dose-dependent, and this holds true for all species. In conclusion, the IL-1 beta and TNF-alpha response by PMs is both species- and dose-dependent.

A functional study on the migration of human monocytes to human leukemic cell lines and the role of monocyte chemoattractant protein-1

In the present study the migration of human monocytes towards the supernatants of five different human myeloid leukemic cell lines, four different human lymphatic leukemic cell lines and blasts derived from three different patients with acute myeloid leukemia (AML) was studied and the role of monocyte chemoattractant protein (MCP)-1 was established with an ELISA assay. Large differences in migration of monocytes towards the leukemic cell supernatants were shown (variation of approximately 10 to 150% compared to positive control), but high amounts of monocyte migration was always restricted to myeloid leukemic cells (cell lines or patient blasts). MCP-1 turned out to play a major role in the migration, firstly since there was a direct correlation between the amount of migration and the concentration of MCP-1 in the supernatants, and secondly since the addition of anti-hMCP-1 was able to inhibit migration to background level in all cases. Cytotoxicity experiments with a MTT test using MCP-1-stimulated monocytes against two human myeloid leukemic cell lines showed no increase in cell death compared to unstimulated monocytes. It is concluded that monocyte migration towards leukemic cells is restricted to the myeloid lineage and is regulated by MCP-1, which is produced in different amounts by the leukemic cells. Besides, MCP-1 does not increase the direct toxic effects of monocytes on leukemic cells.

Ontogeny of milky spots in the human greater omentum: an immunochemical study

BACKGROUND

Milky spots in the human greater omentum are preformed specific accumulations of primarily macrophages within the stroma of the greater omentum. To obtain a better understanding of milky spots in the human greater omentum, the development and the earliest forms of milky spots in the human greater omentum were studied, with special attention to the macrophage population.

METHODS

Specimens of human greater omentum were obtained from fetuses of 20 to 40 weeks gestation and one newborn three days old (n = 6). Using mature macrophages (RFD 7), activated macrophages (RFD 1), B-lymphocytes (CD 22), and T-lymphocytes (CD 2), and immunoperoxydase labeling, the percentage of these cells in developing milky spots and the development of milky spots were studied by light microscopy. A time-dependent increase in the percentage of positive staining cells and the size of clusters was analyzed using the non-parametric Spearman rank correlation test.

RESULTS

Small accumulations of cells with about 50% monocytes/macrophages were present at 20 weeks of gestation. With increasing gestational age the number of clusters of cells increased significantly (P < 0.01) as well as their size (P < 0.01). Starting at 29 weeks, vascularized clusters of cells were seen; true milky spots were present at 35 weeks. A significant (P < 0.05) increase in the percentage of mature macrophages was found in developing milky spots, whereas no activated macrophages were seen. The percentage of B-lymphocytes and T-lymphocytes found in the clusters of cells and milky spots increased significantly (P < 0.05) but did not exceed 10% of the total number of cells.

CONCLUSIONS

From our data it can be concluded that milky spots are specific structures in the greater omentum formed between the 20th and 35th week of gestation. Further, we concluded that immature cells (promonocytes) mature locally in developing milky spots.

Granulocyte macrophage colony stimulating factor pretreatment induces an increase of rat Kupffer cells with enhanced cytotoxicity in vitro and prevention of tumor outgrowth in vivo

Male Wag rats were pretreated for 7 days with 1000 U/ml recombinant murine granulocyte macrophage colony stimulating factor (rmGM-CSF). Rat Kupffer cells (KC) were isolated by a enzymatic method. We injected decreasing numbers of CC531 tumor cells in the portal system. Mean KC yield increased from 1.5 +/- 0.2 to 2.2 +/- 0.2 (p < 0.05). Mean percentage of KC-mediated cytotoxicity against CC531 increased from 20.0 +/- 0.5 to 42 +/- 1.0 after rmGM-CSF (p < 0.05). At 1 x 10(5) CC531 tumor cells we demonstrated prevention of formation of small foci of CC52+ tumor cells. We demonstrate increased isolated KC with enhanced cytotoxic capacity after rmGM-CSF. rmGM-CSF induced prevention of minimal residual disease in the rat liver.

Omental milky spots in the local immune response in the peritoneal cavity of rats

BACKGROUND

Milky spots have been described as reactive structures, their classification varying from inflamed or haematopoietic tissue to lymphoid organs. In this study we investigated the reactivity of the milky spots in the omentum of rats upon induction of a chronic immune response in the peritoneal cavity.

METHODS

At different time points after intraperitoneal administration of Bacillus Calmette-Guérin (BCG), a peritoneal lavage was made, and the omentum and the draining parathymic lymph nodes were taken out. The cellular composition of these tissues was examined on the light microscopic level, using a panel of monoclonal antibodies, and also by electron microscopy.

RESULTS

During the first 4 months after administering BCG, the number and size of the milky spots increased enormously. Separate macrophage, T, and B cell areas were formed, but interdigitating cells and follicular dendritic cells were not observed. The number of cells in the peritoneal cavity also increased, and the cellular composition showed a strong similarity with that of the milky spots. Especially during the onset of the experiment, most bacteria were observed in the macrophages in the milky spots rather than in the draining lymph nodes. A cellular immune response was observed in the parathymic lymph nodes but not in the milky spots.

CONCLUSIONS

Milky spots, either unstimulated or stimulated, should be classified as perivascular infiltrates. They play a role in the initial clearance of bacteria from the peritoneal cavity. Although the large increase in cell number is predominantly caused by immigration of cells, the results do support the role of milky spots as a site for local proliferation and maturation of especially macrophages and also B cells. The obtained data, however, do not support the earlier made assumption that milky spots function as a secondary lymphoid organ in the peritoneal cavity.

The role of BCL-2 and bax protein in monocyte-mediated apoptosis in human leukemic cell lines

Monocytes or monocyte-derived supernatants are able to kill leukemic cells via apoptosis, thereby preferentially effecting more mature leukemic cells. In the present study, the relationship between apoptosis and the apoptosis related proteins, bcl-2 and bax, was investigated in a number of human leukemic cell lines. Monocyte-derived supernatant induces extensive apoptosis in U937 myeloid leukemia cells and minor apoptosis in HL60 cells. No apoptosis was seen in four other cell lines (THP1, HL60-D3, KG1, and K562). The expression of bcl-2 and bax protein was determined in both groups of leukemic cell lines by flow cytometry (bcl-2 and bax) and Western blotting (bcl-2) at baseline level and after incubation with monocyte supernatant after different time periods. No clear relation was found between baseline bcl-2 or bax protein expression and the occurrence of apoptosis after incubation with monocyte supernatant. After different incubation time periods, no change was found in bcl-2 protein expression in U937 and K562 cells, whereas in KG1, HL60, and especially in THP1 cells, a significant decrease could be noticed. On the other hand, there was an increase in bcl-2 expression in HL60-D3 cells. Bax protein expression, measured at the same time points, remained essentially unchanged in HL60-D3 cells, decreased significantly in U937, HL60, and THP1 cells and slightly in K562 cells, and increased significantly in KG1 cells. Also, the ratio bax/bcl-2 decreased in HL60D3, but especially in U937 and HL60 cells, increased slightly in THP1 and KG1 cells, and remained essentially unchanged in K562 cells. Rh-tumor necrosis factor-alpha (TNF-alpha), the main mediator of monocyte mediated cytotoxicity, induced apoptosis in U937, HL60, and THP1 cells, thereby showing changes in bcl-2 expression similar to those found for monocyte derived supernatants. We concluded that in human leukemic cell lines, there is no relation between either bcl-2 or bax protein expression or the ratio of both, and apoptosis mediated by monocyte derived supernatant or TNF-alpha.

Identification of the major chemokines that regulate cell influxes in peritoneal dialysis patients

To investigate which members of the recently discovered family of chemotactic cytokines (chemokines) are important in leukocyte recruitment to a bacterial inflammation site, four different chemokines in the effluent of peritoneal dialysis patients suffering from acute bacterial peritonitis were measured. The presence of two neutrophil-attracting chemokines, interleukin-8 and human melanoma growth-stimulating activity (huGRO alpha), and two monocyte-attracting members of the chemokine superfamily, monocyte chemotactic protein-1 (MCP-1) and regulated on activation normal T cell expressed and secreted (RANTES), was investigated in patient effluents just before, during, and after a peritonitis episode. This was studied in seven peritonitis effluents of five patients by using chemokine-specific enzyme-linked immunosorbent assays. Cell populations in the dialysates were differentiated on cytocentrifuge preparations. The contribution of the detected chemokines to neutrophilic and monocytic cell influxes in the inflamed peritoneal cavity was analyzed by correlating concentrations of chemokines to the relevant cell numbers present in the dialysates of these patients. The detection of the neutrophil-attracting chemokine interleukin-8 during peritonitis was in accordance with other studies. Moreover, a second neutrophil chemoattractant, huGRO alpha, was identified in vivo. Both were elevated during inflammation (P < 0.02) and contributed significantly to the neutrophilic cell influx (P < 0.05). One of the monocyte-attracting chemokines, RANTES, could not be detected in any of the effluents, whereas the other, MCP-1, was significantly elevated during peritonitis (P < 0.02). In contrast to the other chemokines measured, MCP-1 concentration was relatively high in steady-state peritoneal dialysates. An absolute correlation between dialysate MCP-1 concentration and the number of macrophages in these effluents was absent. However, in a 48-well chemotaxis assay, monocyte migration toward peritonitis, as well as steady-state patient dialysates, could be blocked with antibodies to MCP-1. It was concluded, therefore, that MCP-1 is the most important monocyte chemoattractant in peritoneal dialysis steady-state and peritonitis patients; whereas, besides interleukin-8, huGRO alpha was identified as a major neutrophil-attracting chemokine in the peritonitis situation.

Detection of CD 14 on migrated monocytes by specific antibody: a possible quantification for blood monocyte chemotaxis

In the present study we investigated the possibility to use antigen-antibody recognition for detection of monocyte chemotaxis in the 48-well microchamber assay. The described method is based on recognition of cell-specific antigenic determinants present on the migrated monocytes. After conventional 48-well chemotaxis, the migrated cells were incubated with an antibody against the monocyte surface marker CD14 (3C10 hybridoma). Subsequent incubation with enzyme-coupled antibodies and their substrate allowed the antigen and hence the migrated cells carrying this antigen, to be detected and measured in a microplate reader. Our results show that chemotaxis of normal blood monocytes towards the monocyte chemoattractants FMLP and MCP-1 could be detected with the anti-CD14 antibody 3C10 in combination with a horse-radish peroxidase coupled antibody, and that the optical density is a measure for cell number per well (positive correlation, r = 0.95). Incubation of monocytes with the applied chemoattractants FMLP and MCP-1 did not change the CD14 expression as was determined by FACScan analysis. Therefore we conclude that it is possible to use antibodies directed against antigenic determinants like CD14 to detect blood monocyte migration in a more objective way compared to subjective counting of cells on a filter. Eventually, this method can be valuable, especially for chemokine research since chemokines exert their effects on specific target cell populations. By varying the detection antibody, other cell populations besides monocytes may be quantified.

Immunological response in laparoscopic surgery

Immunological response to surgical trauma may be protected during laparoscopic surgery. A less surgical trauma, in comparison with conventional surgery, may explained these important advantages. Plasma and macrophages studies have demonstrated that laparoscopic cholecystectomy causes less depression of cell mediated immunity than open cholecystectomy. What will be the impact of this immunological protection in laparoscopic advanced and oncological surgery? Experimental studies have showed that laparoscopic techniques in advanced and oncological surgery may have important advantages concerning the "preservation of the immune status" of the patient. That will imply in the future a lower percentage of infections, local recurrence and even a lower percentage of distant metastases. On the other hand, the appearance of tumor implants in the port sites after laparoscopic resection for cancer is a significant drawback of this procedure. Proper investigations have to be carried out in order to find the cause and the solution of this dilemma.

Ingestion of Staphylococcus aureus, Staphylococcus epidermidis, and Escherichia coli by human peritoneal mesothelial cells

In the present study we examined whether mesothelial cells can ingest and digest bacteria. The results showed that all strains were ingested. Ingested staphylococci proliferated abundantly, and only a few were digested. Escherichia coli, however, was digested during the first 8 h, whereafter the mesothelial cells disintegrated and proliferation of bacteria could be observed. The clinical implications of these findings are discussed.

Intraperitoneal interleukin-8 and neutrophil influx in the initial phase of a CAPD peritonitis

OBJECTIVE

To investigate whether or not a change in dialysate interleukin-8 (IL-8) concentration precedes the onset of clinically overt peritonitis and is significant in the recruitment of granulocytes during continuous ambulatory peritoneal dialysis (CAPD)-related peritonitis.

DESIGN

CAPD patients stored their overnight effluent at 4 degrees C, which was routinely thrown away after 2 days. If peritonitis developed, patients delivered their effluent of the preceding two nights and the peritonitis effluent for analysis. A control study was performed 1 to 3 months after recovery. Dialysate samples were analyzed for number of cells, differential cell count, IL-8 and elastase concentrations, and their neutrophil chemoattractive capacity. In addition, serum samples during peritonitis were analyzed for IL-8 concentrations.

RESULTS

Ten peritonitis episodes in 7 patients were analyzed. Numbers of neutrophils and levels of dialysate IL-8 and elastase started to increase 4 to 12 hours before the first peritonitis effluent. The dialysate/serum IL-8 ratio was 423.5 during peritonitis and 7.0 in the postperitonitis controls. There was a significant correlation between the number of neutrophils and IL-8 concentration in the dialysate. The in vitro neutrophil chemotaxis was increased toward the peritonitis effluents, as compared to control effluents. Incubation of the peritonitis effluents with anti-IL-8 monoclonal antibody blocked the increase in neutrophil chemotaxis above control levels by an average of 26.7%.

CONCLUSION

IL-8 is produced in the peritoneal cavity during CAPD treatment and may mediate part of the neutrophil recruitment and degranulation in the initial phase of a CAPD peritonitis.

Role of Kupffer cells in arresting circulating tumor cells and controlling metastatic growth in the liver

Metastasis to the liver is a common event in clinical oncology. Blood-borne tumor cells (TCs) arriving to the liver sinusoids run into a special vascular bed. The lining of liver sinusoids is shared by Kupffer cells (KCs) and endothelial cells. KCs, liver-fixed macrophages, are responsible for detection and removal of "non-self" particles. To investigate their role in arresting blood-borne TCs and controlling tumor growth, we injected a syngeneic colon carcinoma cell line into a mesenteric vein of two groups of rats; one group was without Kupffer cells and the other normal controls. We removed the liver of these animals at different time intervals and performed immunohistochemical analysis with monoclonal antibodies (MoAbs) against our tumor cell line, three macrophage subpopulations, natural killer cells, and B and T lymphocytes. Additionally, we showed in vitro spontaneous cytotoxicity of KCs against our tumor cell line. Results suggest that KCs play a relevant role in arresting circulating TCs at the liver sinusoid, although it is limited to a small number of malignant cells. They also seem to play a major role in clearing neoplastic cells from the liver parenchyma, in controlling tumor growth in the very early stages of metastatic development, and in modulating the host immune response to cancer cells.

Effect of intraperitoneal administration of granulocyte/macrophage-colony-stimulating factor in rats on omental milky-spot composition and tumoricidal activity in vivo and in vitro

Milky spots in the greater omentum are small accumulations of leucocytes that consist mainly of macrophages and have recently shown to be a selective dissemination site of intraperitoneal (i.p.) inoculated tumour cells. However, milky-spot macrophages show tumoricidal activity and may, therefore, be an excellent source of effector cells suited for local immunotherapy. In the present study we first examined whether granulocyte/macrophage-colony-stimulating factor (GM-CSF) treatment of isolated milky-spot macrophages affects the cytotoxicity against syngeneic colon carcinoma cells (CC531) in vitro. Secondly, we studied the influence of intraperitoneal GM-CSF administration on the number and antitumour activity of milky-spot and peritoneal macrophages. All studies were performed in Wag/Rij rats in which a syngeneic colon carcinoma cell line (CC531) is available. The results of the in vitro study showed that GM-CSF treatment of the omental macrophages led to an increased cytotoxicity against the tumour cell line. Intraperitoneal administration of 1000 U GM-CSF daily for 7 consecutive days demonstrated both an enhanced antitumour activity of the milky-spot macrophages and an increase in the milky-spot macrophage population. An increase in the proliferative capacity, according to bromodeoxyuridine incorporation, was shown in the milky-spot macrophages. Taking into account both the enhanced macrophage number and their enhanced activity upon i.p. GM-CSF treatment, the milky-spot macrophages may provide a rationale for local intraperitoneal immunotherapy in the prevention of intra-abdominal tumour growth.

Role of Kupffer cells in arresting circulating tumor cells and controlling metastatic growth in the liver

Metastasis to the liver is a common event in clinical oncology. Blood-borne tumor cells (TCs) arriving to the liver sinusoids run into a special vascular bed. The lining of liver sinusoids is shared by Kupffer cells (KCs) and endothelial cells. KCs, liver-fixed macrophages, are responsible for detection and removal of "non-self" particles. To investigate their role in arresting blood-borne TCs and controlling tumor growth, we injected a syngeneic colon carcinoma cell line into a mesenteric vein of two groups of rats; one group was without Kupffer cells and the other normal controls. We removed the liver of these animals at different time intervals and performed immunohistochemical analysis with monoclonal antibodies (MoAbs) against our tumor cell line, three macrophage subpopulations, natural killer cells, and B and T lymphocytes. Additionally, we showed in vitro spontaneous cytotoxicity of KCs against our tumor cell line. Results suggest that KCs play a relevant role in arresting circulating TCs at the liver sinusoid, although it is limited to a small number of malignant cells. They also seem to play a major role in clearing neoplastic cells from the liver parenchyma, in controlling tumor growth in the very early stages of metastatic development, and in modulating the host immune response to cancer cells.

Omental milky spots in the local immune response in the peritoneal cavity of rats

BACKGROUND

Milky spots have been described as reactive structures, their classification varying from inflamed or haematopoietic tissue to lymphoid organs. In this study we investigated the reactivity of the milky spots in the omentum of rats upon induction of a chronic immune response in the peritoneal cavity.

METHODS

At different time points after intraperitoneal administration of Bacillus Calmette-Guérin (BCG), a peritoneal lavage was made, and the omentum and the draining parathymic lymph nodes were taken out. The cellular composition of these tissues was examined on the light microscopic level, using a panel of monoclonal antibodies, and also by electron microscopy.

RESULTS

During the first 4 months after administering BCG, the number and size of the milky spots increased enormously. Separate macrophage, T, and B cell areas were formed, but interdigitating cells and follicular dendritic cells were not observed. The number of cells in the peritoneal cavity also increased, and the cellular composition showed a strong similarity with that of the milky spots. Especially during the onset of the experiment, most bacteria were observed in the macrophages in the milky spots rather than in the draining lymph nodes. A cellular immune response was observed in the parathymic lymph nodes but not in the milky spots.

CONCLUSIONS

Milky spots, either unstimulated or stimulated, should be classified as perivascular infiltrates. They play a role in the initial clearance of bacteria from the peritoneal cavity. Although the large increase in cell number is predominantly caused by immigration of cells, the results do support the role of milky spots as a site for local proliferation and maturation of especially macrophages and also B cells. The obtained data, however, do not support the earlier made assumption that milky spots function as a secondary lymphoid organ in the peritoneal cavity.

Renal function influences interleukin-8 background production by cultured human mesothelial cells

Previous studies have demonstrated that mesothelial cells (MC) are important in the local host defense system of the peritoneal cavity. Most studies on the function of MC are performed on MC derived from material of patients with normal renal function (NRF). The aim of the present study was to examine differences in interleukin (IL)-8 expression by MC from patients with NRF and from patients with end-stage renal disease (ESRD). Therefore, MC were isolated from the omentum and pleural exudate of patients with NRF, from spent effluent of stable peritoneal dialysis (PD) patients, and from omentum obtained during catheter implantation prior to PD treatment. MC were stimulated with increasing doses of IL-1 beta or tumor necrosis factor-alpha for 24 hours, after which the supernatant was analyzed for IL-8 content. The IL-8 background level of MC isolated from patients with NRF was significantly lower than the IL-8 background level of MC derived from patients with ESRD. Although IL-8 production appeared to be higher in the ESRD MC, this difference was not significant after stimulation. While the overall immunity is depressed in uremia, MC are activated. The relatively high background of IL-8 might lead to an insensitivity of neutrophils by blocking the receptors and explain their impaired chemotaxis in uremia.

The combination 5-fluorouracil/levamisole induces enhanced rat Kupffer cell-mediated cytotoxicity in vitro against the syngeneic colon adenocarcinoma cell line CC531

The mode of action of the combination treatment 5-fluorouracil (5-FU) and levamisole in colorectal cancer patients is unknown. It is postulated that the beneficial effect may be explained by an immunomodulatory effect on Kupffer cell (KC) cytotoxicity. We evaluated the effect of levamisole (200 micrograms/ml) and 5-FU (10 microM) on rat KC cytotoxicity against syngeneic CC531 tumor cells. Viability of KCs was unaffected by 5-FU and/or levamisole. The combination did not enhance growth inhibition of CC531 compared to 5-FU alone. A significant increase in KC cytotoxicity was observed after 24-hr incubation with 5-FU/levamisole especially at an effector/target ratio of 10 (P < 0.05). 5-FU alone had no effect on KC cytotoxicity, while levamisole induced only a slight increase. Our in vitro data suggest that the additive effect of the combination 5-FU/levamisole on KC cytotoxicity may attribute to the beneficial effect of the adjuvant treatment in colorectal cancer patients.

Phagocytosis and killing of suspended and adhered bacteria by peritoneal cells after dialysis

OBJECTIVE

To determine the effect of dialysis fluid containing various glucose concentrations on the phagocytosis and killing of Staphylococcus aureus by rat peritoneal cells under conditions mimicking the in vivo situation.

DESIGN

Phagocytosis and killing were evaluated by quantitation of the killing capacity of macrophages after in vivo phagocytosis of the bacteria as well as by an in vitro flow cytometric assay of the phagocytosis and killing of adhered bacteria by peritoneal cells.

ANIMALS

Male Wistar rats.

MAIN OUTCOME MEASURE

It was expected that the intraperitoneal administration of dialysis fluid would impair the capacity of peritoneal cells to eliminate bacteria.

RESULTS

The first test revealed no effects of glucose concentration or dwell time on the killing of phagocytosed bacteria by macrophages, median percentages ranging between 29% and 64%. In the second series of experiments no effect of glucose concentration on the phagocytosis and killing of adhered bacteria was found either; however, longer dwell times significantly enhanced both the phagocytosis (at a dwell time of 1 hour, under 20%; at dwell times of 4 or 18 hours, above 20%, p < 0.02) and the killing (at a dwell time of 1 hour, under 53%; at dwell times of 4 and 18 hours, above 70%, p < 0.01).

CONCLUSIONS

Glucose concentration has no effect on the phagocytosis and killing of Staphylococcus aureus, whereas the dwell time significantly enhances both of these functional capacities of peritoneal cells if the bacteria are adhered to surfaces.

Interleukin-8 production by human mesothelial cells after direct stimulation with staphylococci

Mesothelial cells (MC) are able to produce interleukin-8 (IL-8) after stimulation with IL-1 beta or tumor necrosis factor alpha. The aim of our study was to investigate whether MC are able to produce IL-8 after direct stimulation with clinically relevant bacteria. We observed a significant IL-8 response by the MC which were directly stimulated with viable staphylococci.

Enhanced human Kupffer cell-mediated cytotoxicity after activation of the effector cells and modulation of the target cells by interferon-gamma: a mechanistic study at the cellular level

In this study we demonstrate enhanced Kupffer cell (KC) cytotoxicity against several colorectal cell lines by activation of KC and by modulation of the targets (SW948, WiDR, HT29, and SW620) with IFN-gamma. We demonstrated that soluble TNF-alpha had no effect on these tumor cells, while cytotoxicity against SW948 and WiDR was blocked by anti-TNF-alpha. Experiments using a transwell system stressed the importance of close intercellular contact for this process. Anti-IL-1 did not inhibit cytotoxicity against SW948. Modulation of HT29, WiDR, and SW948 by IFN-gamma (500 U/ml) induced a significant increase in cytotoxicity. We conclude that cell-associated TNF-alpha may be responsible for KC cytotoxicity against SW948, a process requiring close intercellular contact. WiDR is only partly lysed by a TNF-alpha-dependent mechanism, whereas HT29 is not. Furthermore, IFN-gamma is involved in the regulation of tumor susceptibility.

Fresh colorectal tumor cells isolated from individual patients differ in their susceptibility to monocyte mediated cytotoxicity

Studies on monocyte/macrophage mediated cytotoxicity usually pertain to the use of cell lines that are liable to antigenic and structural changes. Therefore we compared monocyte mediated cytotoxicity against colorectal tumor cell lines (WiDR, HT29, SW620, and SW948) with fresh colorectal tumor cells from patients. Fresh tumor cells were isolated from surgical specimens by a short enzymatic treatment (Collagenase/DNAse). Monocytes were obtained from one healthy donor. Cytotoxicity was determined using the MTT-assay. Fresh colorectal tumor cells displayed a similar differential susceptibility to cytotoxic monocytes as cell lines. Cytotoxicity against fresh tumor cells ranged from 4.9% to 50.4% at E/T ratio 5 (n = 9). Activation of monocytes with Interferon-gamma (100 U/ml) induced an increase of 6.2% +/- 1.6 (n = 4, P = 0.06). In this study we demonstrate monocyte mediated cytotoxicity against colorectal tumor cells isolated from individual patients. This may be important in view of the development of adoptive immunotherapy and cell-directed immunotherapy.

Novel isolation and purification method permitting functional cytotoxicity studies of macrophages from milky spots in the greater omentum

Milky spots in the greater omentum are well organized perivascular infiltrates of leukocytes which are probably involved in the clearance of tumor cells from the peritoneal cavity. In milky spots, macrophages are the predominant cell type forming a distinct population of cells. To investigate whether these macrophages have a function in the control of metastatic spread in the peritoneal cavity, a novel isolation and purification method was developed in order to study the functional cytotoxicity of macrophages from milky spots in the greater omentum against tumor cells in vitro. In order to obtain a cell suspension, greater omenta of unstimulated healthy male WAG/RIJ rats were incubated in collagenase/DNase suspension and filtered. Subsequently, macrophages were isolated and purified using flow cytometry by sorting unstained cells on the basis of size and internal complexity. Macrophages and other cells were identified by routine May-Grünwald-Giemsa staining and by immunophenotyping with the specific macrophage monoclonal antibody ED 1. Furthermore, macrophage subtypes were characterized by ultrastructural analysis. Functional cytotoxicity of the isolated macrophages was assayed against the syngeneic CC 531 tumor cell line in a colorimetric MTT assay. From three greater omenta of healthy rats 1.16 +/- 0.16 x 10(6) macrophages were isolated with a purity of 83 +/- 2% and a viability of > or = 96%. The macrophages were of the exudate (monocytic), exudate-resident and resident cell type and were in equal proportions. The contaminating cells were mainly mesothelial. A maximum cytotoxicity of approximately 30% was reached with the macrophage fraction at an effector-to-target ratio of 10. Furthermore, it was established that the mesothelial cells did not exhibit cytotoxicity.

Effect of glucose in dialysis fluid on antibacterial defence in the peritoneal cavity

To study the effect of glucose concentration and dwell time of dialysis fluid on peritoneal antibacterial defence, an experimental infection with Staphylococcus aureus was induced in rats. For this purpose rats were inoculated intraperitoneally with Staphylococcus aureus at different intervals after the administration of various dialysis fluids. Twenty-four hours later the numbers of bacteria and cells in the peritoneal cavity were determined. The number of bacteria was correlated positively with the glucose concentration. Furthermore, an inverse correlation between dwell time and the number of bacteria was observed. Neither finding could be attributed to a glucose-dependent growth of the bacteria or disruption of the killing capacity of peritoneal cells in vitro. A glucose-dependent increase in the volume of the peritoneal fluid could partially explain the differences found in vivo. It is concluded that the glucose in dialysis fluid impairs antibacterial defence in the peritoneal cavity and that longer dwell times enhance this defence.

Isolation and purification of large quantities of fresh human Kupffer cells, which are cytotoxic against colon carcinoma

A new rapid method is described for the isolation and purification of functional active human Kupffer cells without the need of in situ perfusion techniques. Liver wedge biopsies (3 to 5 g), obtained after laparotomy, were incubated with pronase under continuous pH registration. Human Kupffer cells were subsequently separated from other nonparenchymal cells by Nycodenz gradient centrifugation and purified by counterflow centrifugal elutriation. Kupffer cells, 1.7 +/- 0.4 x 10(6) per gram liver, were isolated with a purity of 95% +/- 3%. Cell-mediated cytotoxicity of Kupffer cells was assayed against a human colon carcinoma cell line (SW948). Kupffer cell cytotoxicity was 42% +/- 9% (mean +/- SD) at an effector-to-target cell ratio of 10 and significantly increased to 73 +/- 17% (P < .05) after activation of Kupffer cells with interferon-gamma. In conclusion, a reliable and relatively simple method is provided to isolate and purify fresh human Kupffer cells in large yields, which show spontaneous as well as gamma-interferon-induced cytotoxicity against a human colon carcinoma cell line.