Methods for the separation, purification and measurement of nine components of hemolytic complement in guinea-pig serum

Complement-mediated vasoconstriction and graft rejection

The hyperacute rejection of renal allografts has much in common with pig-to-dog renal xenograft rejections. An analysis of the xenograft model revealed new functional aspects of graft rejection that appear to be an integral part of the humoral immune injury. Anaphylatoxin or C5a, a cleavage product of the fifth complement component was shown to play a major role in the rejection of isolated kidneys; it was generated in pig and dog serum by activation of the complement system and caused severe Vasoconstriction in the renal vasculature. It is suggested that histocompatibility antibodies and complement may affect allograft survival via this potent mediator.

Molecular analysis of the membrane attack mechanism of complement

The molecular arrangement of the membrane attack mechanism of complement was explored. The molar ratios of the components within the C5-9 assembly on the target cell surface were determined using human complement proteins in highly purified and radiolabeled form. With the aid of monospecific complement antisera it was possible to probe the spatial relationships between the components of the assembly. C5 and C6, in the presence of C7, were bound to EAC1-3 in equimolar quantities irrespective of the amounts and the relative proportions of C5, C6, and C7 offered. The amount of C8 bound to EAC1-7 increased with input and at saturation of all C8 binding sites the molar ratio of bound C8/bound C5 approached 1.0. Uptake of C9 by EAC1-8 increased with input and at saturation of all C9 binding sites the molar ratio of bound C9/bound C8 became 6.0. However, calculations suggest that the binding of three C9 molecules to one C8 molecule is sufficient to achieve a full hemolytic effect. Evidence was obtained indicating that binding and hemolytic function of C9 depends upon cooperative interaction of multiple C9 molecules. Binding of C8 to EAC1-7 and the generation of hemolytic C8 sites were inhibited by antibody to either C5, C6, or C7. Uptake of C9 by EAC1-8 and the generation of hemolytic C9 sites were strongly inhibited by anti-C8 and to a lesser degree by anti-C5. Binding of C9 (but not hemolysis) was also reduced by antibody to C6 or C7. The data are consistent with the concept that the fully assembled membrane attack mechanism of complement consists of a decamolecular complex: a trimolecular arrangement composed of C5, C6, and C7 forms the binding site for one C8 molecule which in turn furnishes binding sites for six C9 molecules, saturation of three sites apparently being sufficient for expression of full cytolytic activity of the complex. This work made it possible to design a simple molecular model.

Modulation of function of the activated first component of complement by a fragment derived from serum. I. Effect on early components of complement

An activity designated Kf can be separated from human serum and shown to give a 100-300% enhancement in the hemolytic activity of fully activated, fractionated C1. The enhancement of C1 activity is not because of activation of precursor C1 and it is not attributable to an effect on C1 binding. EAC42 or EAC4 intermediates interacted with C1Kf exhibit a greater T(max) and shorter Z(max) than when such intermediates are reacted with the same number of hemolytic units of C1. C3 consumption by the EAC1Kf42 intermediate greatly exceeds that of the EAC142 intermediate produced from the same EAC4 cells by comparable inputs of the other two complement components. Taken together, these findings suggest that Kf-treated C1 achieves more efficient utilization of C4 and C2 to create a larger number of 42 sites as appreciated on the intermediates by shorter T(max) and a greater Z(max), and an increased capacity to utilize C3. The capacity of Kf to enhance C1 upon introduction into whole serum of a patient with hereditary angioedema (HAE) in a manner comparable to its effect on fractionated C1 suggests that the effect of Kf may be pertinent to certain pathophysiologic conditions of man.

Specific inactivation of the fourth complement component. II. In vitro studies

The fourth complement component (C4) inactivator obtained from nurse shark serum was used to inactivate C4 in fresh sera of various mammalian species. These hemolytically inactive sera, which contained the remaining eight complement components in unaltered form, were used (i) as a source of the first complement component (C1) for the generation of sensitized sheep erythrocytes (EA)-C1 and (ii) as a homologous reagent for the measurement of C4 activity with EA-C1 or EA in fresh, normal serum of guinea pigs, humans, dogs, and pigs.

In vitro studies of complement function in sera of C4-deficient guinea pigs

In vitro studies were performed utilizing sera from a strain of guinea pigs with a total absence of hemolytically active C4. Previous studies in these animals have demonstrated normal complement-dependent inflammatory reactions, suggesting that they are able to bypass their deficiency of C4. In vitro studies with C4-deficient serum also indicate normal activation of late-acting C components. Thus, endotoxin was capable of fixing normal amounts of the late components of complement (C3-9) in these sera, but did not fix C1 and C2. Antigen-antibody complexes fixed both early and late components of complement, although components beyond C4 were fixed less efficiently than in normal sera. Therefore, both in vivo and in vitro evidence indicates that the C4-deficient guinea pigs possess an alternate pathway for activation of late-acting complement components. Antigenic analysis of C4-deficient serum utilizing both guinea pig anti-C4 antibody and rabbit anti-C4 antibody suggests an absolute deficiency of C4-like molecules. Sera from animals with C4-deficiency were found to have one-half the normal level of C2. Sera from five of eight animals tested had 10-20% normal C1 activity. C3-9 assayed as a complex was normal.

C1r, subunit of the first complement component: purification, properties, and assay based on its linking role

A method to obtain C1r, a subunit of the first complement component, in a highly purified state has been described for the first time. The stepwise method starts with a neutral euglobulin precipitation, after diethylaminoethyl- and carboxymethyl-cellulose chromatography and a final preparative polyacrylamide electrophoresis step. Such C1r preparations are devoid of C1q and C1s activities and show only one protein band on analytic polyacrylamide electrophoresis. Rabbits injected with this preparation produced antisera showing only one precipitation band. The stability of C1r activity was determined under different conditions, and C1r was found to be labile at 37 degrees C, pH 7-8 and low ionic strength. The electrophoretic mobility of purified C1r is that of a beta-globulin on disc acrylamide electrophoresis and on agarose electrophoresis at pH 8.6. Its molecular weight as estimated by sephadex chromatography is 168,100.A sensitive hemolytic assay based on the property of C1r to link C1s to C1q and thereby to generate macromolecular C[unk]1 is described. The number of C[unk]1 molecules generated is stoichiometrically related to the concentration of C1r for a fixed C1q and C1s concentration provided that the titration is carried out below the plateau zone. Macromolecular C1 can be separated from free C1s as the former is cell bound. This method of purification and assay should allow the development of monospecific antisera and further chemical study of C1r.

Complement and complement-like activity in lower vertebrates and invertebrates

A purified cobra venom factor with C-inhibiting activity also promotes lysis of erythrocytes in fresh mammalian serum. Lysis-inducing activity of purified cobra venom factor was found in sera of lower vertebrates including the cyclostome hagfish and in invertebrates. Lysis-inducing activity was most effective with frog serum. Frog serum was found to be more hemolytic for E(s) in the presence of CVF than when cells were sensitized with hemolysin. The hemolysis induced by CVF with frog serum, as in the higher vertebrates, was inhibited when sera were pretreated with known C inhibitors including heat, chelators, endotoxin, immune complexes, and CVF itself. Complexes formed with CVF and either frog serum or invertebrate hemolymph promoted lysis of indicator cells in the presence of frog serum in EDTA. This lysis was most marked when the starfish-CVF complex was used and was C-dependent. Conversely, complex formed with frog serum and CVF promoted lysis of E in the presence of invertebrate hemolymph (Limulus) in EDTA. Hence, serum components were to some degree at least interchangeable between vertebrate sera and invertebrate hemolymph. Lysis-inducing activity of purified CVF occurs in a wide range of species, has revealed activities resembling those of terminal C-components in lower vertebrates and invertebrates, and provides one means for study of C and C-like activities in primitive species.

Lysis of erythrocytes by complement in the absence of antibody

A new pathway of complement-mediated hemolysis has been described. It is independent of antibody and does not require binding of the first four complement components to the target-cell surface. The actual attack of the target cell begins with the attachment of C5, C6, and C7. The binding reaction is catalyzed by C4, 2, 3, an enzyme which may be formed in cell-free solution. C4, 2, 3 may effect binding of C5, 6, 7 by acting from the fluid phase or from the surface of another cell to which it is specifically bound (EAC 4, 2, 3). In either case, the resulting product is EC5, 6, 7 which is susceptible to lysis by C8 and C9. Erythrocytes from patients with paroxysmal nocturnal hemoglobinuria (PNH) were particularly susceptible to lysis by the above described mechanism. PNH cells, but not normal human erythrocytes, could also be lysed through activation of complement by cobra factor. These observations allow the operational distinction of an activation and an attack mechanism of complement.

The fixation of complement and the activated first component (C1) of complement by complexes formed between antibody and divalent hapten

Hapten-antibody complexes prepared at equivalence with the bivalent hapten bis-DNP-octamethylene-diamine and purified rabbit anti-DNP antibody were fractionated by Sepharose gel-filtration and the fractions examined by electron microscopy. Individual fractions were tested for whole-complement fixation and C1 fixation. Dimer forms did not show this type of biological activity, while fractions containing tetramers and larger polymers exhibited both C and C1 fixation, which could be inhibited by prior exposure of the complexes to the univalent hapten epsilon-DNP-caproic acid. The dose-response result indicated that the C-fixation observed was not due to interpolymeric cooperative effects. It was concluded that in the generation of biological activity by soluble antigen-antibody complexes made with complement-fixing antibody, quaternary structural changes following specific combination with antigen may be as important as any tertiary structural alterations that occur in the individual immunoglobulin molecule.

Reactive lysis: the complement-mediated lysis of unsensitized cells. I. The characterization of the indicator factor and its identification as C7

This paper describes the characteristics of the indicator factor (I) which takes part in reactive hemolysis and its identification as the seventh component of complement. I was shown to be a beta globulin with a sediment coefficient of 5.7S and a molecular weight of about 140,000. Experiments on the depletion of I activity with anti-I antiserum or with activated R euglobulin showed that I was a late acting complement component necessary for the lysis of cells after the EAC142 stage. Complement component analysis of purified I fractions excluded all known components except C7. The physicochemical characteristics of I are compatible with published data on C7. The method of quantitation described represents a convenient method of testing for C7.

Deficiency of C1r in human serum. Effects on the structure and function of macromolecular C1

THE EXPERIMENTS PRESENTED HERE UTILIZE A HUMAN SERUM MARKEDLY DEFICIENT IN HEMOLYTIC COMPLEMENT ACTIVITY TO SHOW THAT: (a) The hemolytic deficiency is the result of a selective deficiency in hemolytic C1. (b) The relative absence of hemolytic C1 is due to a profound deficit in C1r function associated with less than normal C1s protein and hemolytic function and normal C1q protein concentration and function. This deficit in C1r in the face of normal C1q suggests that different cell types are responsible for the synthesis of each of these components. (c) Whatever the basis for the deficiency of C1r function, this defect results in an inadequate association of the remaining C1 subcomponents, C1q and C1s, even in the presence of calcium ions, thus suggesting that C1r has an important role in the assembly and/or maintenance of macromolecular C1.

Complement system in synovial fluids from patients with rheumatoid arthritis

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Neutralization of sensitized virus by purified components of complement

Herpes simplex virus which had been sensitized with immunoglobulin M antibody was neutralized by serum deficient in the fifth and sixth components of complement (C) but not by serum deficient in the fourth component C (C4). The sequential addition of the functionally purified components of C showed that the activated first component of C (C1[unk]) failed to neutralize sensitized virus. However, in the presence of an optimal concentration of C1[unk], the addition of C4 resulted in neutralization. The amount of virus neutralized was dependent upon the concentration of immunoglobulin M used to sensitize the virus and the concentration of C1[unk] and C4. The addition of the second component of C (C2) to reaction mixtures containing an optimal concentration of C1[unk] and a limiting concentration of C4 resulted in increased neutralization and the amount of virus neutralized was dependent upon the concentration of C2. The addition of the third component of C (C3) to reaction mixtures containing an optimal concentration of C1[unk] and limiting concentrations of C4 and C2 also resulted in increased neutralization and the amount of virus neutralized was dependent upon the concentration of C3.

Structural polymorphism of the fourth component of human complement

The fourth component of human complement (C4) in 102 individual plasma samples has been examined by the technique of antigen-antibody crossed electrophoresis (AACE). Electrophoretic heterogeneity of C4 was manifested by the repeated occurrence of seven different precipitin patterns. These patterns were formed by varying combinations of three subtypes of C4, differing in electrophoretic mobility. The subtypes were designated C, A, and A(1), in order of increasing electrophoretic mobility toward the anode. The evidence that the observed electrophoretic heterogeneity of the C4 molecule represents structural polymorphism rests on five points: the pattern obtained from the plasma of a given individual was reproducible in different runs and with different bleedings; all seven patterns could be demonstrated on the same electrophoretic run; C4 of a given subtype retained its characteristic mobility after purification, when run alone or mixed with plasma containing C4 of other subtypes; the subtypes A(1) and C comprising pattern 6 could be separated chromatographically as well as electrophoretically; and the characteristic relative mobilities of different C4 subtypes, in plasma or after purification, were retained even after the rather large shift in mobility associated with conversion to C4i. The ratio of C4 hemolytic activity to protein concentration varied according to the subtype composition of individual samples, with highest ratios occurring with patterns composed of subtype C alone, intermediate values with patterns consisting of A and C, and lower values occurring with patterns containing subtype A alone. Although the mechanism of inheritance of this polymorphism is not yet clear, the data suggest that subtypes A and A(1) are inherited as autosomal codominant characteristics, independent of the inheritance of subtype C.

Heat labile opsonins to pneumococcus. II. Involvement of C3 and C5

When encapsulated type 25 pneumococci (Pn25) were opsonized with normal guinea pig serum, they consumed much more C3 than other complement (C) components. Fixation of C3 to the organisms was demonstrated by radio-labeling techniques, and its capsular localization was established by the use of monospecific anti-C3 antibody. Treatment of the serum with an appropriate dose of a purified cobra venom factor (VF) destroyed C3 and all of the opsonic activity, without appreciably affecting the other C components. Addition of purified C3 completely restored the opsonic activity of the VF-treated serum, indicating a requirement for C3. Since purified C3 alone had no opsonic activity, it was concluded that the C3 molecules had to be cleaved (to C3b) to function as opsonins. Experiments with C5-deficient mice revealed that C5 also plays a definite, but quantitatively less impressive, role in antipneumococcal defense.

The requirement of serine esterase function in complement-dependent erythrophagocytosis

The p-nitrophenyl ethyl phosphonate esters have been shown to inhibit complement-dependent erythrophagocytosis when exposed to guinea pig polymorphonuclear leukocytes prior to the initiation of phagocytosis. Inhibition of phagocytosis occurred in a manner characteristic of the well-defined capacity of phosphonate esters to inactivate serine esterases: inhibition was irreversible, dependent upon the temperature of reaction and pH of the reaction medium, and proportional to the concentration of inhibitor used and the duration of exposure between leukocytes and inhibitor. Phosphonate inhibition was further shown to be independent of any general cell damaging effects of the compounds used. The phagocytic enzyme inhibited by phosphonate esters apparently exists in or on leukocytes in an already activated state prior to the initiation of the phagocytic process. The inhibitory profile of the activated phagocytic esterase was found to be essentially identical to the profile of inhibition previously obtained for the activated chemotactic esterase of rabbit polymorphonuclear leukocytes, suggesting that the same enzyme may function in both chemotaxis and phagocytosis. Various substrates including acetate esters reported to protect the activated chemotactic esterase from inhibition by phosphonate esters did not exhibit a clear protective effect in the phagocytic system and attempts to define the relationship between the two enzymes were unsuccessful. Suggestive evidence was also obtained for the requirement of the function of a second, activatable esterase in the phagocytic process.

Fluid phase destruction of C2hu by C1hu. II. Unmasking by C4ihu of C1hu specificity for C2hu

It has been demonstrated that C1 isolated in the unactivated form fails to inactivate C4 or C2 in the fluid phase, while the activated molecule, C1 rapidly converts C4 to hemolytically inactive C4i, but does not efficiently inactivate C2. The production and presence of C4i now confers on C1 the ability to rapidly inactivate C2. After heating at 56 degrees C, so as to destroy the hemolytic activity, heat inactivated C1 is still capable of inactivating C4 but the presence of C4i no longer confers an ability to inactivate C2. Studies with the subunits of C1-C1q, C1r, C1s, indicate that the action of C1s on C2 can be inhibited by C1r and that this inhibition is reversed by the presence of homologous C4. These studies indicate that the interaction of C4i with a heat labile receptor conformation in C1 uncovers a masked specificity for C2.

Release of trapped marker from liposomes by the action of purified complement components

Liposomes containing trapped glucose marker were prepared from the chloroform-soluble fraction of sheep erythrocyte membranes. These liposomes release glucose when incubated with rabbit anti-sheep erythrocyte serum and a source of complement. Experiments with purified human complement components show that loss of marker is absolutely dependent on the presence of components 2 and 8. An absolute requirement for component 9 cannot be demonstrated, although it stimulates glucose release from the liposomes. These results establish a parallelism between the response of biological membranes and liposomal membranes to antibody and complement.

Neutralization of sensitized virus by the fourth component of complement

Herpes simplex virus which had been sensitized with IgM antibody was not neutralized by the addition of the purified activated first component of complement. In the presence of an optimum concentration of the first component of complement, however, the sensitized virus was neutralized by the addition of a high concentration of the purified fourth component of complement. Under these conditions, the addition of the purified second and third components of complement failed to enhance virus neutralization. With low concentrations of the fourth component of complement, the addition of the second and third components enhanced virus neutralization.

Natural immunity to bacterial infections: the relation of complement to heat-labile opsonins

Heat-labile opsonins to pneumococci in normal mammalian sera, unlike antibodies, fail to interact with the bacteria at 0 degrees C and require Ca(++) and/or Mg(++). They are readily removed from serum by antigen-antibody complexes that fix complement (C) and are inhibited by reagents that inactivate various C components. The principal heat-labile opsonin to pneumococci is activated C3 (C3(b)), but a slight enhancing effect is exerted by one or more of the late-reacting components of the hemolytic complement system (C5-C9). Since heat-labile opsonins are immunologically polyspecific, they presumably play a broad protective role in the early (preantibody) phase of acute bacterial infections.

A specific inactivator of mammalian C'4 isolated from nurse shark (Ginglymostoma cirratum) serum

A material which specifically inactivates mammalian C'4 was isolated from low ionic strength precipitates of nurse shark serum. The C'4 inactivator was not detected in whole serum. The conditions of its generation and its immunoelectrophoretic behavior seem to indicate that it is an enzymatically formed cleavage product of a precursor contained in whole shark serum. The inactivator was partially purified and characterized. It had an S-value of 3.3 (sucrose gradient) which was in agreement with its retardation on gel filtration, was stable between pH 5.0 and 10.0, had a half-life of 5 min at 56 degrees C, pH 7.5, was inactivated by trypsin and was nontoxic. Its powerful anticomplementary activity in vitro and in vivo was solely due to the rapid inactivation of C'4; no other complement components were affected. No cofactor requirement was observed for the equally rapid inactivation of highly purified human and guinea pig C'4. The kinetics of C'4 inactivation and TAME hydrolysis, the greater anodic mobility of inactivated human C'4, and the influence of temperature on the rate of inactivation suggest that the inactivator is an enzyme and C'4 its substrate. This conclusion was supported by the more recent detection of a split product of C'4. Intravenous administration of the C'4 inactivator could prevent lethal Forssman shock and suppress the Arthus reaction in guinea pigs; it prolonged significantly the rejection time of renal xenografts but had no detectable effect on passive cutaneous anaphylaxis. Anaphylatoxin could be generated in C'4 depleted guinea pig serum with the cobra venom factor, but not with immune precipitates. The possible relationship between C'1 esterase and the C'4 inactivator is discussed on the basis of similarities and dissimilarities.

Fluid phase destruction of C2hu by C1hu. I. Its enhancement and inhibition by homologous and heterologous C4

The fluid phase inactivation of C2(hu) by C1(hu) is markedly enhanced by the presence of C4(hu). The enhancement is afforded by C1 inactivated C4(hu), namely C4i(hu), and requires the simultaneous presence of enzymatically active C1. Heterologous C4 of guinea pig origin protects C2(hu) from the inactivation by C1(hu). Thus, in both the fluid phase and on the cellular intermediate, C4(hu) is essential to the specific action of C1(hu) on C2(hu). It is possible that C4i alters C2 so as to present a more suitable substrate to the C1 enzyme or that C4i acts on the C1 to uncover a specificity for native C2.