[Risk factors for the development of pneumonia in multiple injured patients. Results of a prospective clinical trial]. / Risikofaktoren für die Pneumonieentwicklung beim mehrfachverletzten Patienten. Ergebnisse einer prospektiven klinischen Studie.

Pneumonia is the most common infectious complication in multiple trauma patients. In a prospective clinical cohort study, 266 multiply injured patients were examined for the development of pneumonia. Various risk factors were tested in uni- and multivariate analyses. Three different definitions of pneumonia were used in order to examine how results depended on definition. The incidence of pneumonia was 41%, but varied with definition (30-50%). Injuries to the thorax, head,and abdomen were associated with a significantly increased risk of pneumonia (adjusted relative risk: 1.77, 1.97,and 1.52, respectively).Furthermore, increasing age led to a higher risk of pneumonia. Although the primary analysis revealed a higher pneumonia risk in male patients (adjusted relative risk: 2.23; 95% CI: 1.43-3.05), this result could not be consistently reproduced when using other definitions of pneumonia. Trunk and head injuries and age are proven risk factors for developing posttraumatic pneumonia. The association between male gender and an increased rate of infectious complications remained questionable.

Pneumonia in multiple injured patients: a prospective controlled trial on early prediction using clinical and immunological parameters.

OBJECTIVE AND DESIGN: In a prospective trial 266 multiple injured patients were included to evaluate clinical risk factors and immune parameters related to pneumonia. METHODS: Clinical and humoral parameters were assessed and multivariate analysis performed. RESULTS: The multivariate analysis (odds ratio with 95% confidence interval (CI)) revealed male gender (3.65), traumatic brain injury (TBI) (2.52), thorax trauma (AIS(thorax) > or = 3) (2.05), antibiotic prophylaxis (1.30), injury severity score (ISS) (1.03 per ISS point) and the age (1.02 per year) as risk factors for pneumonia. The main pathogens were Acinetobacter Baumannii (40%) and Staphylococcus aureus (25%). A tendency towards higher Procalcitonin (PCT) and Interleukin (IL)-6 levels two days after trauma was observed for pneumonia patients. CONCLUSION: The immune parameters (PCT, IL-6, IL-10, soluble tumor necrosis factor p-55 and p-75) could not confirm the diagnosis of pneumonia earlier than the clinical parameters.

The effect of additional brain injury on systemic interleukin (IL)-10 and IL-13 levels in trauma patients.

OBJECTIVE: Besides interleukin (IL)-10, accumulating evidence from in vitro studies has indicated a strong antiinflammatory capacity for IL-13. A prospective clinical study was undertaken to assess the influence of additional brain injury on systemic IL-10 and IL-13 levels as markers for the antiinflammatory state in trauma patients. MATERIAL AND METHODS: The course of IL-10 and IL-13 plasma levels from 32 patients with an isolated severe head trauma (SHT), 50 patients with multiple injuries and additional SHT and 39 patients with multiple injuries without SHT was detected using ELISA-technique. Blood samples from 37 healthy blood donors were analysed for control. RESULTS: IL-10 levels were significantly elevated in all 3 injury groups within 3 h after trauma. The lowest initial release was detected in patients with an isolated SHT (Injury severity score; ISS: 18.1 +/- 5.6). No difference could be demonstrated for the IL-10 levels from multiple injured patients with (ISS: 35.3 +/- 9.6) or without additional SHT (ISS: 25.5 +/- 11.7), though there were relevant differences in the ISS. In contrast, the IL-13 plasma levels were not elevated systemically after trauma. CONCLUSIONS: IL-10 but not IL-13 is a detectable antiinflammatory marker in trauma patients with or without brain injury and to a minor degree in patients with an isolated SHT.

[Severe craniocerebral trauma in multiple trauma. An assessment of the interaction of local and systemic mediator responses]. / Das schwere Schädel-Hirn-Trauma beim Mehrfachverletzten. Eine Bestandsaufnahme zur Interaktion lokaler und systemischer Mediatorwirkungen.

Isolated severe head trauma (SHT) or SHT in combination with multiple injuries are important factors for the prognosis of morbidity and mortality in patients suffering from the consequences of accidents. The prognosis mainly depends on the presence of primary mechanic brain injury and the development of secondary brain damage. Causes for the development of secondary brain damage are the intracranial space demand after traumatic injury and edema formation which may result in iscemia, as well as inflammatory processes. Both isolated SHT and polytrauma with or without brain damage may result in a systemic inflammatory response syndrome (SIRS) due to the synthesis of cytokines and other inflammatory mediators which may cause a single or multiple organ failure (MOF). Often the organism is able to survive isolated traumatic injuries and functional disturbances, but in combination or cumulation they may be lethal. The hypermetabolism after SHT is often regarded as an interaction between the central nervous system and the whole organism by the activation of the neuroendocrine axis. In contrast to the consequences of SHT for the whole organism, multiple injuries after polytrauma may affect brain functions, such as the shock dependent disturbance of the brain perfusion accompanied by brain hypoxia which may lead to an aggravated prognosis. Moreover, coagulation, metabolism and fracture healing are influenced by the onset of SIRS as well. Our knowledge about the bidirectional inflammatory interaction between brain and whole organism is still limited. In this context, the effects of secondary surgical interventions which may additionally, stress a traumatized body have to be considered and are the subject for actual clinical discussions and experimental studies. This article tries to summarize some important aspects on this topic.

[Immune paralysis of T-lymphocytes and monocytes in postoperative abdominal sepsis. Correlation of immune function with survival]. / Immunparalyse von T-Lymphocyten und Monocyten in der postoperativen abdominellen Sepsis. Korrelation von Immunfunktion mit Uberleben.

In vitro functions of stimulated peripheral T cells and monocytes were investigate in patients experiencing sepsis following major visceral surgery. Cell culture supernatants were analyzed by ELISA for IL-2, IFN-gamma, IL-4, IL-10, TNF-alpha, IL-1 beta, and IL-12p40. In addition, monocyte HLA class II expression was determined by flow cytometry. T cell secretion of IL-2, TNF-alpha, and in part IFN-gamma (but not IL-4) was significantly diminished in non-survivors throughout the entire course of sepsis, compared to controls and sepsis survivors. Production of IL-1 beta and IL-12 p40 by monocytes was strongly reduced in both survivors and non-survivors at the onset of sepsis. Persistence of depressed monocyte cytokine secretion correlated with lethality. Thus, overall suppression of cytokine production by T cells and monocytes was already observed at the beginning of postoperative sepsis. HLA class II expression by monocytes exhibited a strong and sustained down-regulation with no significant differences between sepsis survivors and non-survivors. In summary, suppression of both T cell and monocyte functions develops early during postoperative sepsis. Recovery of immune functions and severity of immune defects are associated with outcome.

Selective defects of T lymphocyte function in patients with lethal intraabdominal infection.

BACKGROUND: In recent models, compensatory antiinflammatory immune reactions triggered in response to systemic inflammation were considered important for the outcome of sepsis. The present study investigated T-cell functions in patients with postoperative sepsis due to intra-abdominal infection. METHODS: Peripheral T cells were purified from 32 sepsis patients and 41 healthy controls. Proliferation and production of interferon (IFN)-gamma, interleukin (IL)-2, IL-4, tumor necrosis factor (TNF), and IL-10 were stimulated by cross-linking of CD3 and CD28. RESULTS: T-cell proliferation and production of IL-2 and TNF were severely suppressed in patients with lethal intraabdominal infection as compared with survivors and healthy controls. Sepsis survivors showed normal T-cell proliferation and IL-2 release, whereas secretion of TNF was reduced. However, TNF suppression in survivors was less severe than in nonsurviving patients. Defective T-cell functions were observed at the onset of sepsis and persisted throughout the entire observation period. T-cell production of IL-4 and IL-10 was not affected by postoperative intraabdominal infection. CONCLUSIONS: Defective T-cell proliferation and secretion of IL-2 and TNF correlate with sepsis mortality, thus indicating an important role of T 'cells for the immune defense against postoperative infection. Immune defects were evident at the onset of sepsis, suggesting that immunosuppression may develop as a primary response to sepsis without preceding immune hyperactivity.

Downregulation of T helper type 1 immune response and altered pro-inflammatory and anti-inflammatory T cell cytokine balance following conventional but not laparoscopic surgery.

BACKGROUND: The clinical advantages of laparoscopic procedures result from a minimized surgical trauma. The present study was performed to investigate immunosupression following laparoscopic operations as compared with open surgery. Our analysis focused on the T cell secretion of cytokines that regulate the critical balance of either T helper type-1 (Th1)- and Th2-mediated immune responses on pro- and antiinflammatory activities. METHODS: In a prospective study, immunological data of 26 patients submitted to laparoscopic cholecystectomy (LCE) and 17 patients undergoing conventional cholecystectomy (CCE) for symptomatic cholecystolithiasis were compared. Patients with acute cholecystitis and patients developing postoperative complications or receiving immunosuppressive medication were excluded. Production of interferon (IFN)-gamma, interleukin (IL)-2, IL-4, tumor necrosis factor (TNF)-alpha, and IL-10 by isolated T cells stimulated by cross-linking of CD3 and CD28 was evaluated preoperatively as well as on postoperative days 1 and 6 or 7. Cytokines were measured by immunoenzymometric assay. RESULTS: IFN-gamma, TNF-alpha, and IL-2 production by T cells decreased significantly by 48.3%, 36.6%, and 36.8%, respectively, on postoperative day 1 after CCE, but not after LCE. These results indicate severe suppression of Th1-type and proinflammatory cytokines after the open operation. In contrast, IL-4 and IL-10 did not show significant changes in either group suggesting that Th2 cell response and anti-inflammatory activity remained normal. CONCLUSIONS: The present study shows that open, but not laparoscopic cholecystectomy is associated with a marked suppression of T lymphocytes functions as indicated by deregulation of both the Th1/Th2 and the pro-/anti-inflammatory cytokine balance. The results therefore suggest that downregulation of Th1 cell-mediated immune response and pro-inflammatory activity of T cells is a hallmark of open, but not laparoscopic surgery.

Increased susceptibility to postoperative sepsis in patients with impaired monocyte IL-12 production.

IL-12 is a potent immunoregulatory cytokine that is essential for the development of protective immunity, as demonstrated by numerous animal models of infection. Here, we provide evidence for a critical role of IL-12 in human sepsis. The results of a prospective study of 184 patients undergoing major elective surgery of the upper and lower gastrointestinal tract revealed that, in contrast to patients showing uneventful recovery, monocyte IL-12 production was severely and selectively impaired in patients developing postoperative sepsis. Moreover, the extent of monocyte IL-12 suppression correlated with the severity of postoperative sepsis. Monocyte IL-12 secretion was suppressed before surgery and remained low until the onset of sepsis. Therefore, the suppression of IL-12 secretion preceded the onset of postoperative sepsis but did not occur as a consequence of major surgery. In contrast, IL-1beta production was only reduced during the late postoperative course in patients developing postoperative sepsis, and TNF-alpha release was even increased at different time intervals before the onset of sepsis. Thus, reduced IL-12 release does not reflect a general defect in monocyte cytokine production. Consequently, these results establish a critical role for IL-12 in early resistance to postoperative infection and may allow for the development of novel therapeutic strategies designed to stimulate host defense mechanisms and to reduce the incidence and severity of septic complications.

Normal T lymphocyte and monocyte function after minimally invasive surgery.

BACKGROUND: The aim of this study was to evaluate immune defense mechanisms after laparoscopic (LCHE) and open cholecystectomy (CHE), particularly with regard to monocyte and T-lymphocyte function. METHODS: In a prospective study, we evaluated the following immunological data from 27 patients (21 women, six men; mean age, 47.2 years) submitted to elective LCHE and 14 patients (seven women, seven men; mean age, 60.8 years) undergoing elective CHE: T-lymphocyte proliferation (stimulated by SEA, SEB, TSST-1 with antigen presentation by patient monocytes), expression of cell surface molecules on monocytes (HLA-DR, CD80, L-Selectin), CD4+ T lymphocytes (HLA-DR, CD25, ICAM-1, L-Selectin), and granulocytes (L-Selectin). Blood samples were collected preoperatively and on postoperative days 1 and 6-7. Statistical analysis was performed using the Mann-Whitney U test for paired samples. RESULTS: HLA-DR on monocytes significantly decreased after LCHE during the early postoperative course but returned to preoperative levels within 1 week. After CHE, significant downregulation of HLA-DR expression persisted throughout the whole observation period. This decrease, however, did not alter the antigen-presenting capacity of monocytes in both groups. Moreover, the APC-independent proliferative capacity of T lymphocytes was unimpaired. CD25 expression was significantly increased on postoperative day 1 after CHE but not after LCHE. Expression of HLA-DR, ICAM1, and L-Selection on CD4+ T cells was not altered in either group. CD80 on monocytes and L-Selection on monocytes and granulocytes remained unchanged after both procedures. CONCLUSIONS: HLA-DR surface molecules on monocytes that are required for antigen presentation were significantly decreased in both groups; they returned to normal within 1 week after LCHE but not after CHE. However, the antigen-presenting capacity for monocytes remained normal in both groups. T-cell stimulation, reflected by an increase of CD25 expression, was observed only after CHE, not after LCHE. We therefore conclude that LCHE interferes less with immune defense than CHE; however, the clinical relevance of the changes noted after the open operation remains to be determined.

Distinct mechanisms of immunosuppression as a consequence of major surgery.

Altered host defense mechanisms after major surgery or trauma are considered important for the development of infectious complications and sepsis. In the present study, we demonstrate that major surgery results in a severe defect of T-lymphocyte proliferation and cytokine secretion in response to coligation of the antigen receptor complex and CD28. During the early postoperative course, reduced cytokine secretion was observed for interleukin-2 (IL-2), gamma interferon, and tumor necrosis factor alpha, which are associated with the Th1 phenotype of helper T lymphocytes, and for IL-4, the index cytokine of Th2 cells. During the late postoperative course, T-cell cytokine secretion increased to normal levels. Production of the anti-inflammatory cytokine IL-10 was altered, with different kinetics being selectively elevated during the late postoperative course. In contrast, the capacity of peripheral blood monocytes to present bacterial superantigens and to stimulate T-cell proliferation was normal or enhanced after surgery despite a significant loss of cell surface HLA-DR molecules. Thus, the level of major histocompatibility complex class II protein expression does not appear to predict the antigen-presenting capacity of monocytes obtained from surgical patients with uneventful postoperative recovery. Secretion of IL-1beta and IL-10 by endotoxin-stimulated peripheral blood monocytes was increased at different time points after surgery. Major surgery therefore results in a distinct pattern of immune defects with a predominant defect in the T-cell response to T-cell receptor- and CD28 coreceptor-mediated signals rather than an impaired monocyte antigen-presenting capacity. Suppression of T-cell effector functions during the early phase of the postoperative course may define a state of impaired defense against pathogens and increased susceptibility to infection and septic complications.

GTP-binding proteins are involved in the modulated activity of human neutrophils treated with the Panton-Valentine leukocidin from Staphylococcus aureus.

Significant amounts of leukotriene B4 (LTB4) are generated by human polymorphonuclear neutrophils (PMNs) after incubation with the Panton-Valentine leukocidin (Luk-PV) from Staphylococcus aureus V8 strains. We showed that GTP-binding proteins (G proteins) are involved in the Luk-PV-activated signal transduction of PMNs. ADP-ribosylation of heterotrimeric G proteins by cholera and pertussis toxins decreased the Luk-PV-induced LTB4-generation. In contrast, ADP-ribosylation of the low-molecular-weight G proteins rho and rac by Clostridium botulinum exoenzyme C3 increased the Luk-PV-induced LTB4 synthesis. The subsequent stimulation of Luk-PV-treated PMNs by either calcium ionophore A23187, sodium fluoride, or formylmethionyl-leucyl-phenylalanine was significantly inhibited. This decrease was paralleled by a loss of G-protein functions, including GTPase activity and GTP-binding capacity. An increase of G-protein functions was obtained with low amounts of Luk-PV. In addition to the modulated G-protein functions, ADP-ribosylation of 24-, 40-, and 45-kDa proteins by Luk-PV was detected. As shown in control experiments, the ADP-ribosylated 24-kDa proteins were not substrates for C. botulinum exoenzyme C3. Introduction of ras p21 into digitonin-permeabilized PMNs was without effect on subsequent Luk-PV stimulation. In addition, the translocation of ras p21, ras GAP, and 5-lipoxygenase into the membrane of Luk-PV-treated PMNs, as well as the expression of chemotactic membrane receptors for LTB4 and formylmethionyl leucyl phenylalanine, was significantly diminished.

Mouse fibroblasts defective in thrombin mitogenesis possess functional proteolytically activated receptor for thrombin: requirement for a second signaling pathway.

Thrombin mitogenesis in fibroblasts requires two distinguishable subsets of signals; one generated by proteolytic cleavage, the other by high-affinity cell surface binding. Characterizing two closely related mouse embryo (ME) cell lines with high numbers of thrombin binding sites, we found that one line, B11-A, responds mitogenically to thrombin, epidermal growth factor (EGF), and serum, whereas the B11-B cell line is responsive to EGF and serum, but not to thrombin. The B11-B defect responsible for loss of thrombin responsiveness is not due to differences in the number of high-affinity binding sites, the affinity of thrombin binding to these sites, or to differences in cell surface expression of proteolytically activated receptors for thrombin (PART). The defect is also not associated with an inability of thrombin to activate PART since thrombin stimulates the cleavage-dependent induction of the proto-oncogene c-fos in both B11-A and B11-B cells. Various combinations of thrombin, synthetic thrombin receptor peptide, TRP-14 (SFFLRNPGENTFEL), platelet-derived growth factor (PDGF), and phorbol 12-myristate 13-acetate (PMA) were used to better define the defect in thrombin-mediated mitogenesis in B11-B cells. Direct activation of protein kinase C with PMA in combination with thrombin did not overcome B11-B nonresponsiveness. However, mitogenic responsiveness was regained in B11-B cells by simultaneous addition of PDGF and either thrombin or TRP-14. Therefore, the B11-B defect may involve a set of signals initiated by nonproteolytic thrombin interactions distinct from those initiated by PART, but related to the downstream signals initiated by the tyrosine kinase-associated growth factors, EGF and PDGF.

Leukotriene B4 generation and DNA fragmentation induced by leukocidin from Staphylococcus aureus: protective role of granulocyte-macrophage colony-stimulating factor (GM-CSF) and G-CSF for human neutrophils.

We studied the effect of leukocidin from Staphylococcus aureus V8 strains (Luk-PV) on the generation of Leukotriene B4 (LTB4) and its metabolites from human polymorphonuclear neutrophils (PMNs). Significant amounts of LTB4 were generated by PMNs after leukocidin exposure in a time- and dose-dependent manner, as shown by reversed-phase high-performance liquid chromatography analysis. In this regard, the S and F components of leukocidin acted synergistically. The calcium ionophore A23187 induced LTB4 generation, and the metabolism of exogenously added LTB4 into biologically less active omega-oxidated compounds was significantly decreased after leukocidin exposure. Priming of PMNs with granulocyte-macrophage colony-stimulating factor (GM-CSF) or G-CSF prior to leukocidin exposure substantially increased toxin- and calcium ionophore A23187-induced LTB4 formation. The inhibitory effects of leukocidin on mediator release were accompanied by membrane damage and DNA fragmentation, which were both restored after pretreatment with GM-CSF. The data suggest that the presence of costimulatory priming factors such as GM-CSF or G-CSF in the microenvironment of an inflammatory focus determines the pathophysiological effects induced by S. aureus leukocidin.

Induction of heat-shock proteins by bacterial toxins, lipid mediators and cytokines in human leukocytes.

We studied the influence of a lipid mediator (12-hydroxyeicosatetraenoic acid, 12-HETE), cytokines (IL-6 and TNF-alpha) and different bacterial toxins (alveolysin; exfoliative toxin; toxic shock syndrome toxin 1, TSST-1 and erythrogenic toxin A, ETA) on the expression of heat shock proteins (hsps) in isolated human leucocytes. 12-HETE induces the expression of individual heat shock proteins (65- and 83 kDa) protein in human leukocytes (lymphocytes, monocytes, basophilic granulocytes; LMBs). As was shown by Western blotting (anti-hsp72), IL-6 or TNF-alpha induced hsps preferentially in human LMBs and PMNs, respectively. Among the toxins, ETA and TSST-1 were potent inducers of hsps at low toxin concentrations (10 ng/ml). Alveolysin led to the expression of hsps at hemolytic concentrations (1 HU; 700 ng/ml) whereas at subhemolytic concentrations (7 ng/ml), no heat shock response was observed. The induction of heat shock proteins was also accompanied by increased mRNA levels for hsp70 as determined by PCR analysis. In contrast, exfoliative toxin led to a reduction of the hsp signal in PMNs as determined by Western blotting. Finally, it was demonstrated that PMNs which had been pretreated with TNF-alpha and therefore expressed intracellular hsps were more resistant to cytolytic attack by leukocidin than untreated cells.

Staphylococcus aureus toxic shock syndrome toxin 1 and Streptococcus pyogenes erythrogenic toxin A modulate inflammatory mediator release from human neutrophils.

We studied the influence of staphylococcal toxic shock syndrome toxin 1 and streptococcal erythrogenic (pyrogenic) toxin A (ETA) on intact and digitonin-permeabilized human polymorphonuclear granulocytes (PMNs). As was shown by reversed-phase high-performance liquid chromatography analysis, toxic shock syndrome toxin 1 or ETA alone, in the absence of any additional stimulus, did not induce the generation of the chemoattractant leukotriene B4 (LTB4) from PMNs in a wide range of concentrations. In addition, pretreatment of intact PMNs with either toxin potentiated formyl-methionyl-leucyl-phenylalanine (fMLP)- and washed Staphylococcus aureus cell-induced generation of LTB4 in a time- and dose-dependent manner. This increase included LTB4 as well as its inactive omega-oxidated compounds. Further studies revealed evidence that toxin exposure was accompanied by enhanced cellular receptor expression for fMLP as well as for LTB4. The intrinsic GTPase activity of membrane fractions was modulated by both toxins. Short-term incubation with ETA increased the GTPase activity of PMNs up to 141%. Inhibitory effects were obtained when GTP-binding protein functions were stimulated with sodium fluoride (NaF). In addition, specific binding of Gpp(NH)p to GTP-binding protein was inhibited by both toxins during the first 10 min of incubation and was restored at later times of incubation. Our data therefore suggest that both toxins significantly affect the signal transduction pathways of human PMNs, which results in immunomodulatory functions.

Bacterial toxins induce heat shock proteins in human neutrophils.

We studied the influence of different bacterial toxins (alveolysin; toxic shock syndrome toxin 1, TSST-1 and erythrogenic toxin A, ETA) on the expression of heat shock proteins (hsps) in isolated human polymorphonuclear granulocytes (PMNs). As was shown by Western blotting (anti-hsp72) ETA and TSST-1 were potent inducers of hsps at low toxin concentrations (10 ng/ml). Alveolysin led to the expression of hsps at hemolytic concentrations (1 HU; 700 ng/ml) whereas at subhemolytic concentrations (7 ng/ml) no heat shock response was observed. The induction of heat shock proteins was also accompanied by increased mRNA levels for hsp70 as was determined by PCR-analysis.

Regulation of leukotriene B4 generation from human polymorphonuclear granulocytes after stimulation with formyl-methionyl-leucyl phenylalanine: effects of pertussis and cholera toxins.

The effects of holotoxins and toxin subunits from Bordetella pertussis and Vibrio cholerae strains on intact and digitonin-permeabilized human polymorphonuclear neutrophils were studied. Our data clearly demonstrate that formyl-methionyl-leucyl-phenylalanine (fMLP)-induced generation of chemotactic active leukotriene B4 was inhibited by both holotoxins as well as by their isolated enzymatic A protomers. In contrast, the respective binding components (B oligomers) did not affect leukotriene formation. Priming of digitonin-permeabilized neutrophils with either guanylylimidodiphosphate or inositol trisphosphate increased subsequent stimulation with fMLP. In contrast, diacylglycerol decreased fMLP-induced leukotriene B4 formation, but inositol trisphosphate and diacylglycerol had no effect on inhibition mediated by the toxins. In addition, pertussis and cholera toxins reduced the specific binding of [3H]fMLP. Scatchard plot analysis revealed that the observed decrease of peptide binding was due to a reduced number of receptor sites. The fMLP-stimulated [3H]guanylylimidodiphosphate binding and GTPase activity used as parameters for the activation of G proteins were decreased in parallel. These results suggest altered chemotactic receptor numbers and G-protein functions responsible for the toxin-dependent suppression of fMLP-mediated response for neutrophils.

Anesthesia machine malfunction simulating spontaneous respiratory effort.

We present a case in which a dip in the capnogram of an anesthetized patient, which may indicate clinical complications such as spontaneous respiratory effort, was caused by a malfunction of the anesthesia delivery system. The rubber diaphragm of the ventilator relief valve was found to be coated with a sticky substance which may have caused adhesion at the valve seat. This adhesion blocked the flow of excess gas to the scavenging system during exhalation. It was demonstrated that a pressure of 5 cm H2O was needed to overcome this adhesion.

Modulation of leukotriene generation by pertussis toxin.

The purpose of our study was to characterize the properties of the interaction of pertussis toxin with human polymorphonuclear leukocytes for the modulation of leukotriene generation and metabolism. The cells were stimulated with either the Ca ionophore A23187, opsonized zymosan, or the bacterial peptide formyl-methionyl-leucyl phenylalanine. Incubation of the cells with pertussis toxin led to a rapid inhibition of LTB4 generation when formyl-methionyl-leucyl phenylalanine was used as the stimulus, whereas there was no effect with the Ca ionophore and just a low effect with opsonized zymosan. The inhibition of leukotriene generation was dependent on the incubation time, temperature, and pertussis toxin concentration. The effect was not dependent on the presence of calcium. Incubation of the cells with guanosine 5'-O-(3-thiotriphosphate) the stable analog of GTP, led to a time-dependent increase in leukotriene generation induced by formyl-methionyl-leucyl phenylalanine which was abolished by the simultaneous addition of pertussis toxin. Our data suggest that the formyl-methionyl-leucyl phenylalanine-induced generation of leukotrienes is dependent on a GTP-binding protein. The participation of the various G proteins has yet to be elucidated.