Activated Complement Components Research Articles

Complement-mediated acinar cell necroses in pancreatitis induced by basement membrane antibodies.

To study the role of the serum complement system in the early necrosis of acinar cells an acute pancreatitis was produced by injection of basement membrane antibodies into the pancreatic duct of mice and rats. In all animals deposition of complement (C3) and antibasement membrane IgG could be observed in an identical position within areas of acinar cell necrosis. The extent of parenchymal damage and the intensity of complement deposits corresponded to the injected dose of antibodies. The importance of cytolytically active complement components (C5-9) was demonstrated in congenitally C5-defective old line mice which did not show typical centrolobular necroses 1 hr after intraductal injection of antibodies. However, the normocomplementemic mice developed extensive necroses of acinar cells. The results support the hypothesis of a complement-induced acinar cell necrosis in acute pancreatitis.

Genetics of the complement system.

The complement system, unlike the coagulation system, was largely characterized by in-vitro techniques which did not make use of genetically deficient plasmas. The existence of the genetically deficient plasmas. The existence of the genetically deficient subjects therefore has served largely to increase our knowledge of the in-vivo role of complement. At the present time its clearest role is in the resistance to infection; obviously in the case of C3 deficiency and bacterial infection and possibly more subtly in the case of deficiency of the early active complement components and low virulence organisms. There is so far no evidence that genetic complement deficiency interferes with antibody formation or with the generation of tolerance as has been suggested in the pas (Azar et al, 1968; Dukor and Hartmann, 1973).

Effects on C-reactive protein on the lymphoid system. I. Binding to thymus-dependent lymphocytes and alteration of their functions.

C-reactive protein (CRP) is an acute phase protein which shares with the immunoglobulins the ability to induce precipitation and agglutination reactions and activate the complement system. We report here that purified human CRP binds selectively to human T lymphocytes, inhibits their ability to form spontaneous rosettes with sheep erythrocytes and inhibits their response to allogeneic cells in mixed lymphocyte culture reactions; it fails to inhibit phytohemagglutinin- or concanavalin-A-induced mitogenesis. CRP does not bind to human B lymphocytes, nor does it alter the following B-cell functions: binding to activated complement components or the Fc portion of immunoglobulins, mediation of antibody-dependent cytotoxicity reactions or the ability of allogeneic cells to stimulate a mixed lymphocyte culture reaction. Human CRP shows similar selective binding with murine T lymphocytes. It therefore seems that binding of CRP is a property of T lymphocytes or a subpopulation thereof, and can result in modulation of certain of the T-cell functional characteristics in vitro. We suggest that CRP may play a role in modulating T-cell functions during the inflammatory state.

Phylogeny of Complement Components in Non-Human Primates

The antigenic properties and functional activities of complement components were analyzed in primates to determine their relative evolutionary development. The sera of eight different sub-human primate species were examined by double diffusion in agar and compared to a pool of human serum with rabbit and goat antisera to human complement components Clq, Cls, C4, C2 C3, C5, C6, C8, C9, properdin, factor B (B), and C1 inhibitor. There are no apparent antigenic differences in complement proteins between man and the apes except for C1q. Old world monkeys are antigenically deficient in Clq,C1s, C9, and variably deficient in C4, C3, and C8. New World monkeys are antigenically deficient in all components (measured) except C5, C6, and properdin factor B. Prosimians are antigenically deficient in all components. Functional analyses of complement components showed similar levels in man and primates, except in prosimians. There is a dissociation between hemolytic assays and antigenic analyses, suggesting that functional sites may be separate from antigenic sites.

Complement-independent Clearance of IgG-sensitized Erythrocytes: Inhibition by Cortisone

Abstract The effect of corticosteroid administration on the complement-independent clearance of IgG-sensitized erythrocytes was examined in guinea pigs. 51Cr-labeled guinea pig erythrocytes coated with a known amount of high-avidity IgG antibody were injected into control and cortisone-treated C4-deficient guinea pigs, and cell survival was determined. In these animals with a genetically controlled total deficiency of the fourth complement component, cell-bound antibody does not activate the biologically active complement components; clearance is therefore complement independent. At low levels of sensitization, cortisone completely inhibited the splenic sequestration of IgG coated red cells. As the amount of antibody coating the red cell was increased, higher cortisone doses were required to decrease the rate and magnitude of clearance. Eventually a level of erythrocyte sensitization was reached where cortisone did not significantly alter the clearance pattern compared to untreated controls. The cortisone effect was present by 3 days but required 5-7 days before it was maximal. No evidence was found to suggest that cortisone decreased the affinity of the antibody for the red cell membrane. Rather, the most likely explanation for these results is that cortisone affects the interaction between IgG on the erythrocyte surface and its receptor on splenic and hepatic macrophages. This experimental model of immune hemolytic anemia parallels those cases of warm-antibody-mediated disease in which complement plays no role. These findings suggest that a major clinical effect of cortisone therapy may be to decrease complement-independent erythrocyte clearance, thereby inducing a remission even in the presence of a positive antiglobulin test.

Lymphocyte membrane markers in acute lymphoblastic leukaemia.

Summary. T and B lymphocytes can be detected by specific membrane markers. Spontaneous rosette formation with sheep RBC (E rosette) is a T cell marker, whereas receptors for activated complement component (EAC), for the Fc regions of certain immunoglobulin classes (FcR), and for membrane immunoglobulins (mIg) are specific for B cells. Using these lymphocyte membrane markers we evaluated peripheral blood lymphocytes of 18 patients in different stages of acute lymphoblastic leukacmia (ALL).Our results indicate that in acute untreated ALL there is no set immunologic pattern; instead there is a variety of selective deficiencies. Patients in remission have normal populations of T and B cells, whereas those in relapse present a rather obscure picture.The percentage of lymphocytes with membrane markers was compared to the percentage of blast cells and an inverse relation is observed. This indicates that these are abnormal blast cells.The changes from the untreated acute stage through to remission was followed in one subject, and in two others additional study was performed on bone marrow and spinal fluid lymphocytes.

QUALITATIVE IMMUNOGLOBULIN (Ig) DEFICIENCY, RECURRENT INFECTIONS, AND INTACT CELLULAR IMMUNITY

A 10 year old female has had repeated episodes of bacterial infections including pneumonia, otitis, adenitis, and urinary tract infections. She is short, has lymphadenopathy and a protuberant abdomen. IgG=1500 mg%, IgM=430 mg%, IgA= 68 mg%, IgD 18.5 mg% and IgE=l4 IU/ml. Ig Subclasses, inmunoelectrophoresis and complement component activity are normal. After isolating Group A streptococci from the throat and an excised node, ASO and other streptococcal antibody titers were low or undetectable. The excised lymph node showed reactive hyperplasia. Lymphocyte counts were normal. Blood is Group O and isoagglutinin titers (A and B) were absent. Responses to diphtheria, typhoid and hexavalent pneumococcal vaccine were minimal or absent. Normal numbers of B lymphocytes were determined by membrane immunofluorescence and rosettes. Spontaneous rosette formation with sheep erythrocytes was normal. In vivo delayed hypersensitivity was normal. Normal lymphocyte responses to mitogens and allogeneic cells occurred. Neutrophil (PMN) chemotaxis, mobility, phagocytosis and bactericidal activity were normal. A serum related defect in PMN opsonic and cidal activity with strep and E. coli was reversed with normal serum. The patient appears to represent a profound abnormality of antibody formation associated with recurrent infections.

Activation of the alternate complement pathway by autologous red cell stroma.

The present study demonstrates the ability of human autologous RBC stroma to activate the alternate complement pathway (C3-Activator system, properdin system), as evidenced by the generation of C3-Activator (C3A) from C3-Proactivator (C3PA) when RBC ghosts and sonicated ghosts are incubated with autologous serum. Intact RBC's, hemoglobin, and concentrated platelet stroma, on the other hand, are inactive in this regard. We postulate that this in vitro activity of RBC stroma may occur intravascularly when erythrocytes are damaged by immune or nonimmune mechanisms. The ensuing interaction of activated complement components with platelets leading to release of platelet factor three (PF-3) may constitute a mechanism for activation of the coagulation system during acute hemolytic episodes.

Anti-inflammatory drug mechanisms.

The approach to management of disordered inflammation via pharmacological modification of the chemical mediators thereof is reviewed. Anti-inflammatory drug effects seem unlikely to be exerted to an important degree by way of actions on histamine or serotonin, neither is there any clear evidence that anti-inflammatory drugs achieve their effects by intervening in kinin formation. Activation of complement components is an important influence in the development of the inflammatory process and some aspects may be subject to modification by drugs, e.g. corticosteroids. Lysosomal enzymes are capable of compounding inflammatory reactions if lysosomal membrane integrity is prejudiced. Anti-inflammatory drugs such as steroids and chloroquines may stabilise lysosomal membranes and gold salts may inhibit lysosomal hydrolases. Although an action in uncoupling oxidative phosphorylation is shared by a number of anti-inflammatory drugs, this seems unlikely to be of importance in the conditions operating under therapeutic use. Prostaglandin synthesis in situ has now been shown to be potentially important in medication of inflammation. Non-steroidal anti-inflammatory acidic drugs inhibit prostaglandin bio-synthesis under a variety of conditions, indomethacin being consistently highly active, as are other of the more potent non-steroidal anti-inflammatory agents; aspirin also being effective. Connective tissue activating peptide (CTAP) which can reproduce many of the features characterising rheumatoid arthritis is inhibited by cortisol and a variety of non-steroidal agents. Non-steroidal acidic anti-inflammatory drugs share characteristics such as protein-binding and capacity to displace endogenous substances from serum protein binding sites. However, such displacement capacity is shared by other drugs without anti-inflammatory effects. The inflammatory process is an exceedingly complex reaction made up of numerous interacting systems with a variety of mediators. Relative importance of the various factors changes with the phase of the process. To imagine that the effects of a diverse group of drugs are likely to be attributable to an action at a single specific point is probably ingenuous. However, convincing inhibitory effects on the part of the drugs effective in this context may be seen on several of the specific chemical mediators. It may be the capacity to interfere at several different points in the chain of events involved in the inflammatory reaction that endows effective anti-inflammatory drugs with their special therapeutic properties.

Protective role of smooth lipopolysaccharide in the serum bactericidal reaction.

The mechanism by which smooth lipopolysaccharide (LPS) protects Salmonella typhimurium C5 from the lethal action of specific antibody and complement has been investigated. Tris(hydroxymethyl)aminomethane (Tris) and ethylenediaminetetraacetate (EDTA), which sensitize S. typhimurium C5 to the bactericidal action of immune serum, were shown to cause appreciable structural modification of the smooth LPS associated with these cells. Mg(2+) was shown to reverse the sensitization of C5 by Tris, but this divalent cation was unable to reverse the sensitizing effect of Tris plus EDTA, which, unlike Tris, caused relatively large amounts of O-antigenic components to be released from the C5 cell wall. The possibility that smooth LPS blocks the interaction of activated complement components with receptors on the cell wall is discussed.

Complement and disease. Current concepts.

Important biologic events can be attributed to activated complement components, and studies are under way to establish the contribution of these serum factors in human hypersensitivity and inflammatory diseases of unknown etiology. Technics for collecting quantitative data on these components have recently become available.

RELATION OF A ß1-GLYCOPROTEIN OF HUMAN SERUM TO THE COMPLEMENT SYSTEM

The protein of human serum, tentatively designated beta(1C)-globulin, was shown to possess serological activity and to be related to the complement system. Another serum protein (beta(1A)-globulin) was identified as the inactivated form of beta(1C)-globulin. Incubation of fresh serum with various immune precipitates or with soluble gamma-globulin aggregates at 37 degrees C. resulted in the removal of beta(1C)-globulin. Treatment of fresh serum with zymosan at 17 and 37 degrees C. had a similar effect. In both instances beta(1C)-globulin was removed from serum, apparently by conversion to beta(1A)-globulin. However, isolated beta(1C)-globulin did not react with immune precipitates or zymosan, nor did beta(1C)-globulin of serum previously heated at 56 degrees C. Highly purified beta(1C)-globulin was tested for complement component activity by means of the usual reagents. All of the preparations examined were found to reconstitute the hemolytic activity of guinea pig R(3). However, they failed to reconstitute R(3) obtained from human serum. Isolated beta(1A)-globulin was found to be inactive in all systems. When isolated beta(1C)-globulin in either phosphate or in borate buffer was stored at 37 degrees C., the activity detected by means of guinea pig R(3) declined within 6 days to 20 to 30 per cent of its original value. As the activity decreased, beta(1C)-globulin was gradually converted to beta(1A)-globulin. Addition of beta(1C)-globulin to a limited complement system (human C') caused an increase of both initial velocity and final degree of hemolysis. Although beta(1C)-globulin did not cause lysis of EAC'(1, 4, 2), it fully prevented the otherwise rapid decay of EAC'(1, 4, 2) at 37 degrees C., and so presumably interacted with this complex.