Some relationships among hemostasis, fibrinolytic phenomena, immunity, and the inflammatory response

The Role of the Complement System in the Pathogenesis of Infectious Forms of Hemolytic Uremic Syndrome

Hemolytic uremic syndrome (HUS) is an acute disease and the most common cause of childhood acute renal failure. HUS is characterized by a triad of symptoms: microangiopathic hemolytic anemia, thrombocytopenia, and acute kidney injury. In most of the cases, HUS occurs as a result of infection caused by Shiga toxin-producing microbes: hemorrhagic Escherichia coli and Shigella dysenteriae type 1. They account for up to 90% of all cases of HUS. The remaining 10% of cases grouped under the general term atypical HUS represent a heterogeneous group of diseases with similar clinical signs. Emerging evidence suggests that in addition to E. coli and S. dysenteriae type 1, a variety of bacterial and viral infections can cause the development of HUS. In particular, infectious diseases act as the main cause of aHUS recurrence. The pathogenesis of most cases of atypical HUS is based on congenital or acquired defects of complement system. This review presents summarized data from recent studies, suggesting that complement dysregulation is a key pathogenetic factor in various types of infection-induced HUS. Separate links in the complement system are considered, the damage of which during bacterial and viral infections can lead to complement hyperactivation following by microvascular endothelial injury and development of acute renal failure.

Coagulation and complement: Key innate defense participants in a seamless web

In 1969, Dr. Oscar Ratnoff, a pioneer in delineating the mechanisms by which coagulation is activated and complement is regulated, wrote, “In the study of biological processes, the accumulation of information is often accelerated by a narrow point of view. The fastest way to investigate the body’s defenses against injury is to look individually at such isolated questions as how the blood clots or how complement works. We must constantly remind ourselves that such distinctions are man-made. In life, as in the legal cliché, the devices through which the body protects itself form a seamless web, unwrinkled by our artificialities.” Our aim in this review, is to highlight the critical molecular and cellular interactions between coagulation and complement, and how these two major component proteolytic pathways contribute to the seamless web of innate mechanisms that the body uses to protect itself from injury, invading pathogens and foreign surfaces.

Lanadelumab for the prevention of attacks in hereditary angioedema

Introduction: Hereditary angioedema (HAE) with C1 esterase inhibitor deficiency (C1-INH-HAE) is a rare disease that manifests with cutaneous and/or submucosal swellings due to uncontrolled activation of the contact/kinin system. Attacks recur with unpredictable frequency and severity, laryngeal edema is potentially lethal, and the disease burden may severely disrupt patients' lives.Areas covered: This review provides an overview of lanadelumab, a human monoclonal antibody targeted against plasma kallikrein that was recently approved for prevention of symptoms in C1-INH-HAE.Expert opinion: The phase III HELP Study demonstrated the efficacy of lanadelumab in reducing HAE attacks. These positive results are being further confirmed in the open-label extension study. This agent addresses some of the limitations of existing prophylactic options as tolerability issues, the need for intravenous administration and frequent dosing. Therefore, lanadelumab can profoundly improve the quality of life of patients with C1-INH-HAE.

Polyphosphate: an ancient molecule that links platelets, coagulation, and inflammation

Inorganic polyphosphate is widespread in biology and exhibits striking prohemostatic, prothrombotic, and proinflammatory effects in vivo. Long-chain polyphosphate (of the size present in infectious microorganisms) is a potent, natural pathophysiologic activator of the contact pathway of blood clotting. Medium-chain polyphosphate (of the size secreted from activated human platelets) accelerates factor V activation, completely abrogates the anticoagulant function of tissue factor pathway inhibitor, enhances fibrin clot structure, and greatly accelerates factor XI activation by thrombin. Polyphosphate may have utility as a hemostatic agent, whereas antagonists of polyphosphate may function as novel antithrombotic/anti-inflammatory agents. The detailed molecular mechanisms by which polyphosphate modulates blood clotting reactions remain to be elucidated.

Tracks of a non-main path traveler: 2011 Thomas Willis Lecture

After an unconventional beginning in stroke research, I veered off the main path repeatedly to view problems from a different perspective. In this lecture summary, I would like to return to several points along the byways that led to research with some continuity.

How inflammation modulates central nervous system vessel activation and provides targets for intervention--a personal perspective

I here describe a line of research that grew out of studies of spinal cord-damaging decompression sickness, focused on the blood-endothelial interface, that was influenced by the local Shwartzman phenomenon, addressed innate immune and inflammatory mechanisms, and ultimately arrived at mucosal tolerance approaches to prevent stroke. Intranasal instillation of E-selectin is under development as a novel means of targeting immunomodulation to activating blood vessels within the vascular tree supplying the brain. The goal of this form of focused immunomodulation is to prevent recurrent strokes in patients that have previously suffered transient ischemic attacks or strokes.

Mast cells as early responders in the regulation of acute blood-brain barrier changes after cerebral ischemia and hemorrhage

The inflammatory response triggered by stroke has been viewed as harmful, focusing on the influx and migration of blood-borne leukocytes, neutrophils, and macrophages. This review hypothesizes that the brain and meninges have their own resident cells that are capable of fast host response, which are well known to mediate immediate reactions such as anaphylaxis, known as mast cells (MCs). We discuss novel research suggesting that by acting rapidly on the cerebral vessels, this cell type has a potentially deleterious role in the very early phase of acute cerebral ischemia and hemorrhage. Mast cells should be recognized as a potent inflammatory cell that, already at the outset of ischemia, is resident within the cerebral microvasculature. By releasing their cytoplasmic granules, which contain a host of vasoactive mediators such as tumor necrosis factor-alpha, histamine, heparin, and proteases, MCs act on the basal membrane, thus promoting blood-brain barrier (BBB) damage, brain edema, prolonged extravasation, and hemorrhage. This makes them a candidate for a new pharmacological target in attempts to even out the inflammatory responses of the neurovascular unit, and to stabilize the BBB after acute stroke.

Prevention of the localized and generalized Shwartzman reactions by an anticomplementary agent, cobra venom factor

Both localized and generalized Shwartzman reactions were induced in the same rabbits by simultaneous administration of preparatory intravenous and intradermal doses of endotoxin followed in 24 hr by the provocative dose. Control rabbits with more than 80% positive responses showed corresponding changes of platelet, white blood cell, fibrinogen, and hemolytic complement levels. Circulating fibrinogen and fibrin degradation products were detected shortly after the preparatory dose and persisted for at least 3 days. Rabbits given cobra venom anticomplementary factor showed hypocomplementemia (less than 10% of normal), leukocytosis, and elevated fibrinogen levels. After the administration of endotoxin, only one of 15 CVF-treated animals developed a Shwartzman reaction and that was mild. These rabbits showed only minor changes of platelet and fibrinogen levels throughout the experiment although their white blood cell responses were similar to those of the control group. No detectable fibrinogen and fibrin degradation products appeared in circulation, and the hemolytic complement activity increased gradually beginning with the preparatory dose of endotoxin. Thus depletion of terminal complement components (mainly C3) in rabbits is protective against the development of both localized and generalized Shwartzman reactions; its mechanism of action is probably through the sparing of platelets by inhibiting platelet-endotoxin interaction. The essential role of the complement system in Shwartzman reaction indicates that this coagulopathy probably represents a manifestation of immunologic injury.

Influence of white blood cells on the fibrinolytic response to sepsis: studies of septic patients with or without severe leucopenia

In septic patients capable of normal white cell responses, high plasma levels of PAI-I, t-PA antigen and t-PA-PAI-I complex were observed. The ratios of t-PA and PAI-I were such that free PA activity was almost never observed. In patients severely leucopenic prior to becoming septic the changes were significantly less marked, so presence of leucocytes enhances the fibrinolytic inhibition occurring in sepsis. The non-leucopenic septic group showed greater evidence of thrombin generation in that FPA levels were higher but fibrinogen levels were only slightly less and antithrombin levels not different from those in the leucopenic group. A greater tendency to fibrin deposition and the striking fibrinolytic inhibition noted in patients with normal white cell responses may contribute to the development of some of the complications of sepsis in which fibrin deposition participates and may explain their relative rarity in leucopenic patients. When shock supervened, levels of PAI-I were high in both leucopenic and non-leucopenic groups, indicating that a source of PAI-I outwith the leucocytes themselves contributes to the phenomena observed.

Aprotinin aerosol treatment of influenza and paramyxovirus bronchopneumonia of mice

The therapeutic efficacy of aerosolized aprotinin, a natural proteinase inhibitor, against influenza and paramyxovirus bronchopneumonia of mice is shown. Small-particle aerosol of aprotinin solution was generated by a Collison type nebulizer and infected mice were exposed to aerosol atmosphere by four 30-40 min incubations per day for 6 days. This regimen provided an inhalation aprotinin dosage of approx. 6 micrograms/mouse/day. With such treatment more than 50% of mice infected with lethal doses of either influenza virus or paramyxovirus were protected from death. A suppression of the development of fatal hemorrhagic bronchopneumonia and a normalization of the body weight gain were observed in infected mice treated with aerosolized aprotinin. These data suggest that low doses of aerosolized proteinase inhibitors could be successfully applied against respiratory influenza-like virus diseases.

Induction of procoagulant activity in human epidermal cells

We have studied the induction of procoagulant activity (PCA) by lipopolysaccharide (LPS) in cultured human epidermal cells. Single cell suspensions of epidermal cells were prepared from surgical specimens and stimulated for 24 h with LPS (100 micrograms/ml). PCA was determined by one-stage clotting assay. Stimulation of the epidermal cells with LPS resulted in a significant reduction of the clotting time (approx. 30%) as compared with the nonstimulated controls. Further analysis of the induced PCA showed that it did not require factors of the intrinsic pathway of the clotting cascade (factors XI and XII). Similarly, PCA was not affected by factor IX-deficient plasma but required factors II, VII, and X for its full expression. PCA was inactivated by treatment with phospholipase C but not by heating to 56 degrees C. These data indicate that the epidermal cell PCA resembles tissue factor-like activity, activating the extrinsic clotting pathway. Elimination of Langerhans' cells from the epidermal cell suspension by antibody and complement-mediated lysis did not result in a reduction of PCA in the remaining epidermal cells, indicating that keratinocytes were most likely the producer cells. Induction of PCA on the cell membrane surface of epidermal cells may be an early event resulting in the initiation of a local inflammatory reaction.

Molecular mechanism of complex infection by bacteria and virus analyzed by a model using serratial protease and influenza virus in mice

We examined the effect of a serratial exoprotease on the pathogenesis of influenza virus infection in mice as a model of complicated respiratory infection by bacteria and virus in humans. The 56-kilodalton (56-kDa) protease from Serratia marcescens was administrated intranasally to mice at a dose of 10, 20, or 40 micrograms from day 0 to day 3 after inoculation of the influenza virus. Administration of the protease resulted in remarkable enhancement of the lethal effect of the virus and enhancement of pathological changes in the lungs. Influenza virus replication, determined by plaque-forming assay, was accelerated by the protease. Namely, we found a 100-fold increase in virus yield by day 2. The 56-kDa protease caused generation of plasmin activity in the lungs. In vitro experiments showed that plasmin greatly enhanced the yield of influenza virus, although the effect of the 56-kDa protease by itself was much lower than that of plasmin. Furthermore, the 56-kDa protease could induce plasmin production indirectly via activation of plasminogen by the Hageman factor-dependent cascade in the in vitro system. We conclude that this major serratial exoprotease has a deleterious effect on mice infected with influenza virus and that this effect seems to result from enhancement of viral growth by indirect acceleration of plasmin generation induced by the protease.

Hereditary angioneurotic edema: clinical and laboratory findings in 58 subjects

An in-depth analysis of clinical and laboratory findings in 58 patients affected by hereditary angioneurotic edema (HANE) is reported with special focus on problems related to the diagnosis of the disorder. The functional C1 inhibitor (C1INH) assay is the method of choice in the diagnosis of HANE, as it is capable of revealing the disorder with 100% accuracy. The immunochemical assay of C1INH detected HANE in 84.5% of the cases, i.e., immunochemical deficiency of C1INH (type I HANE). C4 was markedly reduced in both type I and type II HANE; thus, C4 levels can be particularly useful when C1INH functional tests are not available. CH50 testing is of little diagnostic value since total hemolytic complement activity is reduced in a variety of other congenital or acquired pathologies involving the complement system. The CH50 assay after incubation in low ionic strength buffer may be utilized in mass screening programs for qualitative evaluation. However, the test has the drawback of not being applicable in cases of frank hypocomplmentemia. While a depletion of the complement classical pathway was detected in most cases, no alteration in the complement alternative pathway was recorded, nor there was any reduction in immunoglobulin levels. Family history was positive in 100% of the cases. Attacks were almost always brought on by stress and/or trauma, though the causes were sometimes unknown. Edema could be cutaneous (non-pitting and non-pruritic) in 94.2%, laryngeal (often life-threatening) in 48% and abdominal (almost always painful) in 88.4% of patients. Associated pathologies were found in 2 patients, i.e., lupus rash and C3NeF-positive chronic membranoproliferative glomerulonephritis, respectively.

Partial purification of plasma and tissue kallikreins in psoriatic epidermis

Human psoriatic scale extracts produced kinins from heated plasma (11.3 +/- 5.5 ng kinin/mg protein) and from purified low molecular weight (LMW) bovine kininogen (4.4 +/- 1.7 ng/mg). Sephacryl S-200 gel filtration of the extracts showed three peaks of kininogenase activity with Mr values of 90,000 (K-I), 65,000 (K-II), and 35,000 (K-III). Upon DEAE-Sepharose chromatography of the Sephacryl peaks, K-I activity was found in the nonadsorbed fraction and formed kinins only from heated plasma. Peak K-II activity was resolved into two peaks, K-IIa (in the nonadsorbed fraction), which formed kinins only from heated plasma, and K-IIb (in the adsorbed fraction), which formed kinins from both heated plasma and LMW bovine kininogen. K-III kininogenase activity appeared at the same position as K-IIb and also formed kinins from both substrates. Kininogenases K-I and K-IIa had the same Km value (0.3 mM) with Pro-Phe-Arg-p-nitroanilide(pNA), similar to that found with human plasma kallikrein. The Km value of K-IIb with Val-Leu-Arg-pNA (0.8 mM) was like that found for human salivary kallikrein, whereas K-III had a low affinity for this substrate. Like plasma kallikrein, K-I and K-IIa were inhibited by soybean trypsin inhibitor, but only weakly by aprotinin. In addition the kininogenase activity of both K-I and K-IIa was neutralized by adding antihuman prekallikrein immunoglobulin G (IgG). In contrast, K-IIb and K-III were strongly inhibited by aprotinin but not by soybean trypsin inhibitor, consistent with their being tissue kallikreins. It was confirmed that K-IIb and K-III shares antigenic determinant of urinary kallikrein.

Pathogenic factors in the later pulmonary phase of Angiostrongylus cantonensis-infected rats

In rats infected with different worm burdens of Angiostrongylus cantonensis, the loss of body weight was proportional to the increasing dose of infection. Body weight was correlated inversely with female worm burden (r = -0.669), the sum of mean numbers of larvae per gram of faeces (LPG) (r = -0.527) and lung weight (r = -0.761). Lung weight was positively correlated with female worm burden (r = 0.785) and the sum of mean numbers of LPG (r = 0.685). On the other hand, in rats infected with larvae developed from gamma-irradiated first-stage larvae (Experiment B) or infected rats treated with the drug ivermectin (Experiment C), body weight was inversely correlated with the sum of mean numbers of LPG (r = -0.798, Experiment B; r = -0.670, Experiment C) and lung weight (r = -0.862, Experiment B; r = -0.812, Experiment C), but not with female worm burden. Furthermore, lung weight was positively correlated with the sum of mean numbers of LPG (r = -0.783, Experiment B; r = 0.899, Experiment C), but not with the female worm burden. From these results, it is concluded that in the later pulmonary phase of infection in rats the pathogenic effects may be closely related to the increasing number of first-stage larvae produced by female worms.

Identification of proteins adsorbed from human plasma to glass bead columns: plasmin-induced degradation of adsorbed fibrinogen

In a bead column experiment, attempts have been made to identify the proteins adsorbed from plasma onto a glass surface. Proteins adsorbed after a 3-h contact time were eluted sequentially by 1 M tris buffer and SDS. Polyacrylamide gel electrophoresis of eluted proteins showed a multiplicity of components, and not all of these could be identified. Positive identifications were made by immunodiffusion against specific antibodies, band positions on electrophoresis gels, and location of radioactivity in gels when specific radiolabeled proteins were added to plasma. Proteins found were albumin, IgG, fibrinogen, plasminogen, and fibrinogen degradation products (FDP). A major component with an apparent molecular weight of 25,000 remains unidentified. It is unrelated to albumin, IgG, fibrinogen, factor XII, or plasminogen. Adsorbed fibrinogen was less degraded when experiments were performed with plasmas deficient in either plasminogen or factor XII. It is therefore concluded that FDP are formed by activation of adsorbed plasminogen, as was found previously for purified fibrinogen containing a trace of plasminogen. At least part of this activation is potentiated by the contact activation phase of plasma coagulation, in particular activated factor XII.

Cellular and vascular manifestations of cell-mediated immunity

The studies reviewed here emphasize both the complexity and the heterogeneity of cell-mediated immunity. In addition to the round cell infiltrate of the classic descriptions, cell-mediated immunity includes reactions that feature many types of inflammatory cells, that exert profound effects on the blood microvasculature, and that initiate extravascular clotting and, possibly, angiogenesis. The common denominator of all of these reactions is a subset or subsets of sensitized T lymphocytes that, on exposure to specific antigen, recruit and collaborate in other ways with one or more populations of circulating bone marrow-derived cells. Although the reactions generally resemble chronic inflammation by virtue of the lymphocytes and monocytes present, cell-mediated immunity may also take the guise of acute or subacute inflammation when neutrophils or eosinophils predominate and an entirely different morphologic pattern when basophils predominate, as in CBH. Tissue mast cells undergo changes (activation, proliferation) that are generally observed at later stages of delayed hypersensitivity, but no convincing evidence has been presented that these cells play an essential role in the elicitation of cell-mediated immunity. The concept that an essential prerequisite for the elicitation of delayed hypersensitivity is the mast cell-dependent generation of microvascular gaps, favoring inflammatory cell diapedesis, is clearly incorrect. First, lymphocytes fail to traverse certain of the vessels that exhibit such gaps (i.e., those of the SCV) in delayed hypersensitivity reactions in humans. Second, there is no diminution in the cellular infiltration associated with cell-mediated immunity reactions in mast cell-deficient mice. Cell-mediated immunity does not consist of an inflammatory cell infiltrate alone. The local microvasculature is rendered hyperpermeable to varying extents, with resulting extravasation of plasma proteins, including fibrinogen. The majority of extravasated fibrinogen is clotted to cross-linked fibrin, presumably as the result of the actions of procoagulants associated with fixed connective tissue cells and perhaps also because of the activity of infiltrating cells, such as monocytes/macrophages. Clotted fibrin forms a water-trapping gel, which accounts for the induration seen in many delayed hypersensitivity reactions. The microvasculature may also be affected in other ways. Endothelial cells may undergo hypertrophy and cell division or, alternatively, may exhibit profound and progressive injury.(ABSTRACT TRUNCATED AT 400 WORDS)

Degradation of adsorbed fibrinogen by surface-generated plasmin

An investigation of the physical status of fibrinogen that has been adsorbed to glass and then eluted has been conducted. Exposure of Kabi fibrinogen to glass was carried out using a glass bead column experiment. The fibrinogen was eluted sequentially, first by 1 M Tris and then by SDS. The initially eluted fibrinogen showed considerable degradation (SDS polyacrylamide gel electrophoresis) while the later fractions were less degraded. Fibrinogen purified by chromatography on either DEAE-cellulose or Sepharose-lysine to remove plasminogen was less degraded. When purified plasminogen was added to fibrinogen, degradation of column eluates was very extensive in all eluted fractions. These results are interpreted in terms of a surface-mediated activation of plasminogen to plasmin followed by fibrinogenolysis. Although such an effect remains to be demonstrated as a general property of surfaces, it is speculated that surfaces may vary in their activation of fibrinolysis as well as their activation of clotting, and that maximization of fibrinolysis is a worthwhile goal in the development of blood-compatible surfaces.

Activation of latent collagenase by serum proteinases that interact with immobilized immunoglobulin G

It has been previously observed that collagen destruction occurs in the vicinity of immune complexes present in articular cartilages of patients with rheumatoid arthritis. When IgG is covalently linked to Sepharose it behaves as if it has reacted with an antigen to form an immune complex, in that it binds the complement component C1 from human serum. Other serum components also interact with this matrix, though their interaction may not be specific for IgG. Two of these components were shown to possess proteolytic activity, one being kallikrein and the other having the properties of plasmin. Both of the activities could activate latent human collagenase. Whilst the binding of the plasmin activity is probably nonspecific, the binding of the kallikrein activity may be selective for IgG (although it is not certain whether this binding is direct or indirect via another molecule). These results therefore suggest that active proteinases such as plasma kallikrein may be selectively concentrated on immune complexes in vivo, where they may locally activate latent proteinases such as collagenase thereby initiating tissue destruction.

Binding of factors IX and IXa to cultured vascular endothelial cells

Factor IX and its activated form IXa have been found to bind to confluent cultured bovine aortic and human umbilical vein endothelial cells. Binding of bovine factors IX and IXa to the bovine endothelial cells was saturable and specific and reached a plateau in 75 min at 4 degrees C and 30 min at 37 degrees C. Binding was half-maximal at a total factor IX or IXa concentration of 2.3 +/- 0.2 nM. At 4 degrees C, a maximum of 42 fmol of tritiated factor IX or IXa bound to 10(6) cells (an average of 20,000 molecules per cell). The binding of tritiated factor IX or IXa was inhibited by excess unlabeled factor IX or IXa but not by factor X, prothrombin, or thrombin. Competition studies indicated that factors IX and IXa interacted with the same site. Binding was reversible, with 50% of the specifically bound factor IX or IXa eluted in 40 min by a 400-fold excess of unlabeled protein. Specific binding required Ca2+ with half-maximal binding at 1.2 mM CaCl2. Factor IXa bound to the cells was tested for procoagulant activity in a clotting assay with factor IX-deficient plasma, cephalin, and CaCl2. Cell-bound factor IXa was at least 3-fold more active than was factor IXa in solution. The retention of procoagulant activity by cell surface-bound factor IXa provides a mechanism for the localization of clot-promoting activity.

Fibrin as a component of the tumor stroma: origins and biological significance

An association between cancer and the coagulation system was suggested by Trousseau more than a century ago and initial reports of fibrin deposition in the stroma of solid tumors date back some 25 years. However, the validity and generality of these observations have only quite recently been established, and their implications for an understanding of tumor biology, metastasis, and therapy are only now coming to be appreciated by investigators in the mainstream of cancer research. This article reviews the current status of fibrin's role in the biology of tumor growth, considering in turn: (1) the evidence that fibrin is present in tumors, the nature of such fibrin, and its relation to plasma fibronectin; (2) the mechanisms by which fibrin may come to be deposited in tumors; and (3) the potential biological and medical significance of tumor-associated fibrin deposition and degradation. Among the last are such important possibilities as a barrier function to the immune response and possible roles in angiogenesis, desmoplasia, and metastasis.

Demonstration of antiinflammatory activity of fibrinogen and fibrinopeptides in rats

Carrageenin-induced inflammatory rat paw swelling was significantly inhibited by intraperitoneal injection of rat fibrinogen. Whole-body radioscanning of the rat after intraperitoneal administration of 131I-labeled fibrinogen revealed the accumulation of radiolabeled material in the inflammed rat paw. Resorption studies showed that not more than 4% of the intraperitoneally administered [125I] fibrinogen could be demonstrated in the peripheral blood. Furthermore only 1/3 of this circulating radiolabeled protein was able to take part in clot formation, suggesting that inhibition of edema formation is mediated by fibrinogen-derived split products. This is further supported by the finding that rat fibrinopeptides, released by the action of thrombin, also diminish edema formation both after intracardial and intraperitoneal injection into carrageenin-stimulated rats.

Activation of protein mediators of inflammation and evidence for endotoxemia in Borrelia recurrentis infection

Fifteen patients with Borrelia recurrentis infection were studied to evaluate the role of certain plasma proteins and endotoxin in the pathophysiology of both the acute illness and the Jarisch-Herxheimer-like reaction. The causative spirochetes disappeared from the blood during the Jarisch-Herxheimer-like reaction, which occurred about 2 hours after antibiotic therapy. The mean titers of Hageman factor, plasma prekallikrein and serum hemolytic complement activity were decreased at the time of admission and 2 hours after treatment, and rose to normal values during convalescence. Serum properdin titers were decreased in 14 patients at the time of admission, in 12 patients 2 hours after treatment, and in none during convalescence. The frequency of elevated levels of fibrinogen-related antigens increased from three patients at the time of admission to 12 patients 2 hours after treatment. Results of plasma limulus tests for endotoxin-like material were positive in 11 patients at the time of admission and in 13 patients 2 hours after treatment. These findings demonstrated that Hageman factor, prekallikrein and proteins of the complement system are activated in B. recurrentis infection and that endotoxin may play a role in both the acute illness and in the development of the Jarisch-Herxheimer-like reaction after treatment.

Physiopathogenesis of subdural hematomas. Part 1: Histological and biochemical comparisons of subcutaneous hematoma in rats with subdural hematoma in man

The dorsal subcutaneous injection in rats of 12 ml or more of autologous hemolyzed whole blood clotted in situ induced the formation of sterile, hemispheric lesions, 47% of which showed an initial decrease in volume followed by a progressive enlargement. The behavior, histology, and biochemical characteristics of the liquid contents of these lesions were found to be remarkably similar to those of subdural hematomas in man. To evaluate the role of the various blood components that may have influenced the formation and growth of these lesions, more than 150 clots composed of human platelet-free plasma, autologous hemolyzed blood, or autologous whole blood were implanted subcutaneously in rats by either surgical or injection techniques. The in vitro behavior of the different clots used was also assessed. This systematic approach led to the following conclusions: 1) the composition and volumes of the clots are critical variables; 2) plasma-fibrin provides the matrix shape of the lesions; 3) the breakdown products derived from erythrocytes, hemoglobin, leukocytes, and other solid blood elements induce neomembrane formation and contribute to the lesion's subsequent growth; and 4) inflammation mechanisms appear to be essential, while cerebrospinal fluid plays no discernable role in this process.

Morphology of delayed-type hypersensitivity reactions in man

The new morphologic findings reviewed here substantially alter prevalent conceptions of delayed hypersensitivity as a simple cutaneous infiltration of lymphocytes and macrophages. By assigning an integral role of basophils, mast cells, the microvasculature, and the clotting system, the findings have far-reaching implications for an understanding of these clinically important reactions. Morphologic observations, of course, represent only a first step, a foundation on which subsequent immunologic, physiologic, and biochemical experiments can build. Much further work will be required to interrelate these new findings and to integrate them with older observations into a coherent sequence of events which can explain the pathogenesis of cell-mediated reactions. A preliminary attempt in this direction, based on present, rather incomplete information, is presented in Figure 8 as a basis for further investigation.

Endothelial injury induced by bacterial endotoxin: effect of complement depletion

The role of complement activation in the pathogenesis of endothelial injury caused by bacterial endotoxin was investigated in the rat. DNA synthesis in aortic endothelium was compared 48 hours after an intravenous injection of endotoxin (50 - 500 mug) in normal rats and in rats depleted of haemolytic complement by purified cobra venom factor. At the time of endotoxin administration the rats treated with cobra venom factor had less than 3% of the normal haemolytic complement level, their fibrinogen level was increased and clot retraction was impaired. Endotoxin stimulated endothelial DNA synthesis to the same degree in normal and in complement-depleted rats. Cobra venom factor alone did not stimulate endothelial DNA synthesis. The complement-depleted rats given 500 mug endotoxin were less thrombocytopenic than normal rats at the time of sacrifice, but the difference was not statistically significant. We conclude that the injurious effect endotoxin has on endothelium is not mediated by activation of late components of complement.

Induction of macrophage plasminogen activator by endotoxin stimulation and phagocytosis: evidence for a two-stage process

The injection of thioglycollate medium into the peritoneal cavity of the mouse induces high levels of macrophage fibrinolytic activity due to the production and secretion of a plasminogen activator, a trypsinlike serine protease, which is absent in unstimulated macrophages. Intraperitoneal injection of endotoxin or mineral oil can stimulate only a fraction (<10%) of the fibrinolytic activity of thioglycollate cells, similar to the partial stimulation (<10%) seen 1-2 days after phagocytosis of latex or SRBC by unstimulated macrophages. The endotoxin-stimulated macrophages contain and release relatively low levels of plasminogen activator, but these primed cells can be triggered to produce and secrete high levels of enzyme, by phagocytosis of latex. Under conditions where the plasminogen activator is induced and secreted, there are no effects on the production and/or release of lysozyme or intracellular acid hydrolases, Discovery of a two-stage procedure for inducing macrophage plasminogen activator made it possible to study the role of cell priming and phagocytosis separately. Endotoxin was a more effective priming agent, weight for weight, than lipid A:BSA complex. Secretion of the plasminogen activator was induced only by thioglycollate, or endotoxin and latex. In situ fibrinolysis was induced by these agents and mineral oil, BCG, and fetal calf serum, in decreasing order of effectiveness. Phagocytosis of latex in all cases except thioglycollate stimulation, increased fibrinolytic activity from three- to sixfold. Latex and a variety of other particles such as M. lysodeikticus, aggregated gamma-globulin and immune complexes showed dose-dependent stimulation of fibrinolysis by endotoxin-primed macrophages. Although the initial phagocytic trigger was not specific for the substance employed, the ability to induce a sustained response depended on the persistence of the phagocytized particle within the cell. Fibrinolysis and secretion of plasminogen activator continued at high levels for at least 9 days after uptake of latex, a nondigestible particle, whereas plasminogen activator was secreted only transiently after ingestion of rapidly digested M. lysodeikticus. The induction of plasminogen activator secretion provides a mechanism by which the activated macrophage can exert a selective effect on its extracellular environment.