[Expressions of complement C1q and C3c in rat brain tissues with cerebral ischemia/reperfusion injury].

OBJECTIVE: To observe the expression levels of the complement fragment C1q and C3c in rat brain tissues with cerebral ischemia-reperfusion (I/R) injury, and explore the correlation, roles and mechanism of complement reaction and microglia in the brain I/R injury. METHODS: A total of 48 male Sprague-Dawley rats were randomly divided into normal control group, sham group, I/R 24 h, 72 h, 7 d, 15 d model groups. Suture occlusion method was operated to establish focal middle cerebral artery occlusion (MCAO) and reperfusion models. The Nissl staining was applied to observe the structure of neurons, and immunohistochemistry was applied to detect CD11b, C1q and C3c expression. RESULTS: Compared with the sham group, Nissl staining reaction in brain tissues was stronger in the I/R 24 h group, and then became weaker, and the reduction was the most significant in the I/R 72 h group. The expression of CD11b protein increased in the I/R 24 h group and reached the peak value in the I/R 72 h group, followed by gradually reducing. Compared with the sham group, all the model groups were significantly stronger in CD11b expression (P<0.05). C1q and C3c sharply increased in the brain tissue of I/R 24 h group and peaked in the I/R 7 d group, and then presented a downward trend; the differences between the sham group and all the model groups were of statistical significance (P<0.05). CONCLUSION: The expression levels of C1q and C3c are positively correlated with CD11b protein in rat brain tissues with cerebral I/R injury, suggesting that cerebral I/R injury inintiate the brain innate immune response, activates complement C1q and C3c as well as microglia, thus playing the role of protection or damage in cerebral I/R injury.

Complement factors in newly diagnosed Nigerian schizoprenic patients and those on antipsychotic therapy.

The role of Complement factors in the pathogenesis of psychiatric disorders is enormous, but the data on levels and functions of complement factors in patients with schizophrenia are scanty and conflicting. To address this issue, levels of Complement regulators (C1 inhibitor and C3 activator) and complement factors (C1q, C3c, C4 and C5) were determined in the serum of newly diagnosed drug free schizophrenic patients, schizophrenic patients on medication and healthy subjects using immune-plates. C1q was significantly reduced in newly diagnosed schizophrenic patients or schizophrenic patients on medication compared with the controls. C3c was significantly reduced in newly diagnosed schizophrenic patients compared with controls or schizophrenic patients on medication. The levels of C3 activators, C1 inhibitors and C4 were similar in the two groups of schizophrenic patients compared with the controls. It may be concluded from this study that C1q is deficient in schizophrenic patients; and that C3c may differentiate newly diagnosed schizophrenia from schizophrenic patients on medication.

The role of complement in myasthenia gravis: serological evidence of complement consumption in vivo.

BACKGROUND: Antibodies to the acetylcholine receptor (AChR) titin and the ryanodine receptor (RyR) occur in myasthenia gravis (MG). These antibodies are capable of complement activation in vitro. The involvement of the complement system should cause consumption of complement components such as C3 and C4 in vivo. MATERIALS AND METHODS: Complement components C3 and C4 were assayed in sera from 78 AChR antibody-positive MG patients and 52 healthy controls. Forty-eight of the patient sera contained titin antibodies as well, and 20 were also RyR antibody-positive. RESULTS: MG patients with AChR antibody concentrations above the median (11.2 nmol/l) had significantly lower mean C3 and C4 concentrations in serum compared to those with AChR antibody concentrations below the median. Titin antibody-positive MG patients, titin antibody-negative early-onset MG patients, titin antibody-negative late-onset MG patients, and controls had similar C3 and C4 concentrations. Nor did mean C3 and C4 concentrations differ in MG patients with RyR antibodies. Patients with severe MG (grades 4 and 5) had similar C3 and similar C4 levels compared to those with mild MG (grades 1 and 2). CONCLUSION: An increased in vivo complement consumption was detected in MG patients with high AChR antibody concentrations, unrelated to MG severity and non-AChR muscle antibodies.

Stagnant versus dynamic conditions: a comparative adsorption study of blood proteins.

Haemodynamic parameters of flowing blood, such as diffusion, convection, flow and shear rates, are important as they determine the interaction of cells with vessel walls and prosthetic implants in the cardiovascular system. Most of the studies under flow conditions have been performed with platelets or other cells, and less attention has been paid to the effects that these parameters may cause on the adsorption of proteins. For this reason we studied how different shear rates affect the adsorption of human albumin, fibrinogen, total serum proteins, and complement factors 1q and 3c from human serum to silicon surfaces. The most relevant results indicate that during non-flow conditions the amount of adsorbed proteins is always lower than under flow. The different shear rates (225, 915, 1800 and 2700 s(-1)) all gave similar results, indicating that such a parameter is not very critical for single protein deposition. The differences in kinetics of complex protein solutions are conveniently highlighted by use of specific polyclonal antibodies. The difference between non-flow or low shear rate conditions and physiological flow conditions was enhanced for the complement cascade system.

Further characterization of a complement-sensitive mutant of a virulent avian Escherichia coli isolate.

An attempt was made to characterize the mechanism of complement resistance operating in a virulent avian Escherichia coli isolate. Using flow cytometry to detect antibody to C3, we found that there was significantly more antibody bound to a complement-sensitive mutant of this wild type than to the parent organism, suggesting that more C3 subunits were bound to the wild type. Neither the wild type nor the mutant degraded C3. Further, the mutant was phagocytosed to a significantly greater degree than the wild type by cultured phagocytes in the presence of C5-deficient serum. These data suggest that the wild type is resistant to complement, at least in part, because of its ability to restrict C3 deposition on its surface. Therefore, the decrease in virulence seen in the mutant may be related to its increased sensitivity to complement-mediated bacteriolysis or its enhanced susceptibility to complement-opsonized phagocytosis or both.

Activity and activation of the complement system in patients being operated on for cancer of the colon.

OBJECTIVE: To find out if there was any local activation of complement in the vicinity of a colonic cancer, and any fluctuation in the function of the complement system during operation. DESIGN: Prospective study. SETTING: One university and two district hospitals in Denmark. SUBJECTS: 29 selected patients undergoing emergency and elective operations for colonic cancer. INTERVENTIONS: Measurements of systemic and local complement fixation capacity and complement activation in samples of serum or plasma taken before, during, and after operation. MAIN OUTCOME MEASURES: Changes in complement fixation capacity and complement activation during operation. RESULTS: Haemodilution during operation caused a significant reduction in the complement fixation capacity of serum and in the activation of the complement system as measured by generation of C3c. We were unable to confirm the presence of complement inhibitors during operation. Haemodilution caused a 30% reduction in fixation capacity of C3b (12/29 samples of serum had values more than 2SD below the mean of the reference range compared with 4/29 before operation). The activity of C4 was reduced by 25% during operation and the capacity of the complement system to fix C3b and C4b was restored to baseline nine days postoperatively. Concentration of C3d was significantly higher in serum from tumour venous blood compared with that from peripheral blood during operation. CONCLUSION: The presence of complement activation products in the general circulation reflects local activation of the complement system in the vicinity of the tumour, but this may have been influenced by tissue necrosis or subclinical infection. Haemodilution causes a significant reduction in the capacity of the complement system during operation, whereas inhibitory factors associated with the cancer or operation and anaesthesia could not be demonstrated. We found no correlation between complement activity and clinical data.

[Mechanisms and implications of the adhesion phenomenon in Aspergillus fumigatus]. / Mécanismes et implications des phénomènes d'adhérence chez Aspergillus fumigatus.

During the last few years, several works have demonstrated the fixation of different host proteins on Aspergillus fumigatus conidia. Thus, after incubation in the presence of normal human plasma, the C3 component of complement is detected at the surface of conidia. In fact, most of the C3 deposited on conidia is converted in C3b or iC3b which would facilitate their phagocytosis by the macrophages. In the non immune host, the activation of the alternative pathway seems to be the main mechanism of the activation of the complement system by the conidia, but the participation of the classical pathway initiated by the fixation of the C-reactive protein has also been suggested. Aspergillus fumigatus conidia interact also with fibrinogen and laminin. These interactions which are mediated by the D domains of fibrinogen and by the fragment P1 of laminin, are specific. The number of fibrinogen binding sites at the surface of conidia has been calculated to be 1200 by cell, and the dissociation constant 2.2 x 10(-7) M. These interactions could determine the adhesion of conidia to the host tissues as suggested by adherence assays of conidia to proteins immobilized onto wells of microtiter plates. Conidia would bind to the fibrin deposits formed on damaged epithelia in response to the inflammatory reaction, or directly to laminin of the subepithelial basement membrane. Finally, different experiments suggested the identity of the binding sites for C3, fibrinogen and laminin at the surface of A. fumigatus conidia.

Progesterone and RU486 regulation of uterine complement C3 after prior induction with estradiol.

Previous results demonstrated that progesterone (P4) given simultaneously with estradiol (E2) prevented stimulation by E2 of complement C3 expression in the immature rat uterus. Northern blot analysis revealed that simultaneous administration of P4 was able to prevent the E2-stimulated increase in C3 mRNA concentration in the luminal epithelial cells. The purpose of the present investigation was to determine whether progesterone modulates C3 expression after the gene has been induced by prior administration of E2 and also to determine the reversibility of this effect by the concomitant administration of RU38486, 17 beta-hydroxy-11 beta-[4-dimethylaminophenyl]estra-4,9,-dien-3-one (RU486). This regulation was studied by examination of protein synthesis as well as mRNA concentrations. Immature 21-day-old female rats were treated with E2 for 2 days (1 microgram/day), followed 24 h later by P4 (500 micrograms) or vehicle. Uteri were removed 6, 9, and 18 h after progesterone treatment and the radiolabeled secreted proteins were analyzed by SDS-PAGE and immunoprecipitation using a goat anti-rat C3 antibody. In animals treated with vehicle, E2-stimulated C3 synthesis remained elevated at 6 and 9 h and returned to control values by 18 h. In contrast, the administration of P4 resulted in a decrease in C3 synthesis at 6 and 9 h with the greatest decrease observed at 9 h. Similar results were obtained when C3 mRNA concentrations were examined. E2-stimulated C3 mRNA concentrations were decreased in rats treated with progesterone compared to those treated with vehicle alone.2

[Cleavage fragments of C3 and of dermo-epidermal junction of normal human skin]. / Fragments de clivage du C3 et de la jonction dermo-épidermique de la peau humaine normale.

Recently, we have demonstrated the presence of C3dg deposits, a cleavage fragment of the third component of complement, on the basement membrane zone (MB) of normal human skin. These C3dg deposits are specific, isolated and not restricted to stratified squamous epithelia. Their origin is not thought to be due to passive incorporation of circulating C3dg within selected MB. Conversely, human keratinocytes are able to synthesize and secrete C3 and could represent a local source for these C3dg deposits. In situ production of C3 by epidermal cells could play a role in local inflammatory reactions. Similarly, a C3dg binding site(s) in selected basement membrane may account for the accumulation of C3-containing immune complexes in such tissues in pathological conditions.

Levels of complement factor C3 and its activated product, C3a, in operatively salvaged blood.

In intra-operative blood salvage the collected blood is exposed to traumatized tissue and a synthetic circuit. Because of this exposure it was expected that the complement system, which is a contact system present in plasma, would be activated in salvaged blood. To determine whether this occurs, the plasma levels of the complement factor C3 and its activated fragment, C3a, were measured in intra-operative salvaged blood before and after washing. Samples were obtained from patients undergoing aortic surgery where intra-operative salvage was used. In the unwashed salvaged blood, the level of C3 fell (mean C3: 0.33 g/L) and the level of C3a increased (mean C3a: 1994 ng/mL) compared with the patient circulating levels of C3 and C3a (mean C3: 0.70 g/L, mean C3a: 855 ng/mL) respectively. Washing of the collected blood reduced the C3a level (mean: 346 ng/mL) to the patient's level and reduced C3 to the lower detection limit of the test (less than 0.2 g/L). The raised level of C3a and the reduced level of C3 confirm that the complement system is activated and imply that other complement factors are also activated.

Fungal cell adhesion molecules in Candida albicans.

Adherence of Candida albicans to host tissues is considered a crucial step in the pathogenesis of candidiasis. Using in vitro assays, it was demonstrated that the yeast-mycelium transition was an important phenomenon in the acquisition of adhesive properties. Proteins with MWs of 60, 68, 200 and greater than 200 kDa seemed to be involved in germ tube adherence to plastic surfaces. Likewise, recent investigations have revealed that C. albicans expresses on its surface receptors which interact with a wide variety of host proteins, particularly some extracellular matrix components like fibronectin, laminin and collagen. Plasmatic components, such as fibrinogen, iC3b and C3d, have also been proposed as mediators of adherence of C. albicans. Thus, by their reaction with laminin, fibrinogen and C3d, the mannoproteins of 68 and 60 kDa demonstrated multiple biological activities. Proteins of similar MWs were detected as C3d and iC3b receptors, the latter showing similarities with the neutrophil CR3. Based upon the antigenic, structural and functional homologies between the candidal receptors and mammalian integrins, it was postulated that these fungal cell adhesion molecules (F-CAM) are members of the integrin family. Interactions with host proteins and molecular mimicry of mammalian adhesion molecules may be a fertile area for further research.