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

Intravenous immunoglobulin (IVIG) attenuates antibody binding in acute haemorrhagic immunopneumonitis in a rat model of complement-dependent lung injury

Administration of rabbit anti-rat lung serum (PNTS) to rats produces a fulminant haemorrhagic pneumonitis sensitive to the availability of complement. The present experiments were undertaken to assess whether a high dose of IVIG can affect the development of this kind of cytotoxic reaction. The experimental design included groups of Wistar rats pretreated intravenously with physiologic saline, IVIG or a preparation of human F(ab')2 fragments. One hour later the animals were challenged with either saline or PNTS. At 30 min after challenge, blood was collected and the lungs were removed. Pulmonary damage was evaluated by light microscopy; C3 deposits and the binding of immunoglobulins to the alveolar septa were assayed by immunofluorescence. The serum complement activity of the classical and alternative pathways was estimated by a kinetic technique. Pretreatment with IVIG decreased binding of rabbit anti-lung antibodies to alveolar septa and prevented the deposition of C3. These results indicate that pretreatment with IVIG inhibits the binding of the pathogenic antibody to lung tissue. Human IgG binding was not detected in any animal. The protection against lung injury afforded by pretreatment with IVIG, in contrast to the pneumotoxic effect of PNTS observed in control animals, was evident despite the administration of F(ab')2 to the rats. Since pretreatment with F(ab')2 failed to prevent the acute lung lesion, our results indicate that the attenuation afforded by IVIG in this model of complement-dependent tissue injury seems to be related to the integrity of the IgG molecule.

Shark complement: an assessment

The classical (CCP) and alternative (ACP) pathways of complement activation have been established for the nurse shark (Ginglymostoma cirratum). The isolation of a cDNA clone encoding a mannan-binding protein-associated serine protease (MASP)-1-like protein from the Japanese dogfish (Triakis scyllia) suggests the presence of a lectin pathway. The CCP consists of six functionally distinct components: C1n, C2n, C3n, C4n, C8n and C9n, and is activated by immune complexes in the presence of Ca++ and Mg++ ions. The ACP is antibody independent, requiring Mg++ ions and a heat-labile 90 kDa factor B-like protein for activity. Proteins considered homologues of C1q, C3 and C4 (C2n) of the mammalian complement system have been isolated from nurse shark serum. Shark C1q is composed of at least two chain types each showing 50% identity to human C1q chains A and B. Partial sequence of the globular domain of one of the chains shows it to be C1q-like rather than like mannan-binding protein. N-terminal amino acid sequences of the alpha and beta chain of shark C3 and C4 molecules show significant identity with corresponding human C3 and C4 chains. A sequence representing shark C4 gamma chain, shows little similarity to human C4 gamma chain. The terminal shark components C8n and C9n are functional analogues of mammalian C8 and C9. Anaphylatoxin activity has been demonstrated in activated shark serum, and porcine C5a desArg induces shark leucocyte chemotaxis. The deduced amino acid sequence of a partial C3 cDNA clone from the nurse shark shows 50%, 30% and 24% homology with the corresponding region of mammalian C3, C4 and alpha 2-macroglobulin. Deduced amino acid sequence data from partial Bf/C2 cDNA clones, two from the nurse shark and one from the Japanese dogfish, suggest that at least one species of elasmobranch has two distinct Bf/C2 genes.

Animal models for complement deficiencies

The complement system plays a key role in host defense and in the development of autoimmunity. Three types of animal models of complement-mediated disease have traditionally been used: they involve normal animals, animals with spontaneously arising genetic deficiency, and animals treated with complement-inactivating agents. All of these approaches have had partial success in our attempts to understand complement mechanisms. Most animal models of genetic deficiency have been studied relatively little, as the availability of such animals is limited. C4, C2, and partial C3 deficiency in the guinea pig are well characterized, although only C4 deficiency in the guinea pig has been exclusively studied. C3 deficiency in the dog and C6 deficiency in the rabbit are well described, although studies are limited in number. C6 deficiency in the rat has been described recently and C5 deficiency in inbred mice strains has been studied fairly extensively. Factor H deficiency in the Yorkshire pig has also been described. Relatively few agents that inhibit complement are in use. Most widely used in animal studies is cobra venom factor. This inactivates the alternative complement pathway in the fluid phase and thereby depletes complement protein levels. The antigenicity of this protein, purified from the venom of cobras, limits its duration of use in most animal models. Complement-inhibiting agents are rare and, as yet, not widely used. We recently described the use of intravenous immune globulin for inhibiting complement in animal studies and present data on its use in animals, including discordant xenograft rejection, and its potential use in human disease. New developments in molecular biology provide the potential for a vast new array of deficiency models. A limited number of laboratories are actively engaged in the production of animals with inactivated genes. For example, gene knockout mice with no C3, and with no factor B, have been generated. Several complement control proteins have been prepared by genetic molecular biological techniques. Most promising among these is CR1, which limits complement damage in several animal models. Transgenic animals, which complement regulatory proteins expressed on their cells, have been prepared. As complement control proteins tend to be more efficient at regulating complement of the same species type as the regulatory protein, these animals may be useful in such areas as xenograft transplantation. The various animal models are reviewed and their potential application to understanding of human disease is emphasized.

Immunopharmacological approach to Forssman shock

Forssman shock (FS) following the intravenous injection of antisheep erythrocyte antibody into guinea pigs resulted in fatal systemic shock with marked decrease in CH50 values of complement, leucocyte, and platelet counts, and a prolongation of blood coagulation time. In addition, there was an increase in lactate dehydrogenase activity, and decreases in both esterase activity and fibrinogen levels were noted. F(ab')2 of antisheep erythrocyte IgG antibody was not capable of eliciting FS. Cobra venom factor showed a fairly potent inhibition of FS. Leukopenia induced by cytosine arabinoside given intraperitoneally for 5 days had no effect on FS. Colchicine, which decreased the leucocyte count, did not inhibit fatal systemic shock. Administration of heparin or trasyrol did not prevent FS. The present findings demonstrate that FS is inhibited by anticomplementary agents but not by drugs which affect leucocyte and platelet counts, the coagulation system or serum proteases.

Human complement activation by lipopolysaccharides from bacteroides oralis, fusobacterium nucleatum, and veillonella parvula

The properties of different lipopolysaccharide (LPS) preparations to induce C3 conversion in human serum was studied by means of crossed immunoelectrophoresis. C3 conversion by the alternative pathway was evaluated after calcium depletion, and lipid A-dependent activation was measured by means of inhibition with polymyxin B sulfate. LPS from Bacteroides oralis converted Co mainly via the alternative pathway, whereas LPS from Fusobacterium nucleatum and Veillonella parvula const pronounced lipid A-dependent conversion. The results are discussed in relation to the chemical composition of the LPS preparations.

Delayed rejection of cardiac xenografts in C6-deficient rabbits

Puppy hearts were engrafted to C6-deficient rabbits, and also to complement-sufficient animals in order to determine the influence of the sixth component of complement on xenograft rejection. Delayed rejection was observed in the puppy hearts engrafted to the C6-deficient animals indicating that complement sufficiency of C6 is required for hyperacute xenograft rejection.

Interaction of complex polysaccharides with the complement system: effect of calcium depletion on terminal component consumption

Complex polysaccharides and lipopolysaccharides can activate the terminal components of complement by either the classical (antibody, C1, C4, and C2) or alternative complement pathways, but the relative importance of either pathway for terminal component consumption in normal serum is poorly understood. Since classical complement pathway function requires both calcium and magnesium ions, whereas the alternative pathway requires only magnesium ions, selective chelation of calcium ions in serum can be used to block the classical complement pathway while leaving the alternative pathway intact. In these studies, ethyleneglycol-bis-(beta-aminoethyl ether)N, N-tetraacetic acid, a potent chelator or calcium, was used to block the classical complement pathway in normal guinea pig serum. Consumption of the terminal complement components by endotoxin, inulin, and zymosan in such serum was strikingly depressed when compared to serum containing an intact classical complement pathway. These studies demonstrate that in normal serum, both the classical and alternative complement pathways participate in the consumption of the terminal complement components by complex polysaccharides and lipopolysaccharides.

Isolation of C4-synthesizing cells from guinea-pig liver by Ficoll density gradient centrifugation

Cells which synthesize the fourth component of complement have been isolated from guinea-pig liver through rate zonal density gradient centrifugation of suspensions of liver cells on continuous density gradients (2 to 15 per cent) of Ficoll. This procedure separates non-parenchymal cells from parenchymal cells on the basis of size. Cells which synthesized C4 were identified as low density, non-parenchymal cells which comprised only a small proportion of the cells added to the gradient. Phagocytic cells were restricted to the same portion of the gradient as cells which synthesized C4, and there is evidence that cells which synthesize C4 are also phagocytic.

Heterophile antibodies and tissue injury. 3. A role for platelets in the development of lethal vascular injury during Forssman shock in guinea pigs

Platelets appear to be pathogenetic determinants in the development of lethal Forssman shock, which was provoked in guinea pigs by an intravenous injection of rabbit antiserum to sheep erythrocyte stromata. Within moments, circulating platelets (prelabeled with (14)C-serotonin) were removed from the blood stream and impacted in the lungs, where they liberated (14)C into the tissues. When animals were depleted of platelets prior to the production of shock, they survived for prolonged periods of time or were protected against death. Pretreatment with antiinflammatory compounds capable of inhibiting platelet aggregation and release phenomena had a similar protective influence. It would appear, therefore, that Forssman shock is a convenient and accessible model for investigating the mechanisms whereby platelets mediate immune vascular damage.

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.

Heterophile antibodies and tissue injury. 1. Ultrastructure of pulmonary vascular lesions produced by Forssman antiserum in guinea-pigs

The ultrastructural features of pulmonary vascular lesions were studied in guinea-pigs subjected to lethal Forssman shock. Within moments after an intravenous injection of Forssman antiserum the endothelia of venules and capillaries exhibited a wide range of morphological changes. Relatively mild lesions were characterized by the appearance of focal erosions in the cell membrane, cytoplasmic swelling and vacuolization. Severe lesions were associated with overt necrosis and disintegration of the endothelial lining, leaving the basement membrane in direct communication with the intravascular compartment. Platelets and PMN-leucocytes were consistently found to be adhering to denuded or damaged vascular surfaces and forming thromboembolic obstructions within blood channels. These data support the concept that vascular endothelium is a primary target tissue in Forssman shock. In addition, our findings suggest that platelets and PMN-leucocytes may be pathogenetic determinants in the development of Forssman shock.

Prolonged survival of kidney xenografts in leucopenic rabbits

Rabbits rendered leucopenic by means of nitrogen mustard reject kidney xenografts more slowly than normal controls It is therefore probable that polymorphonuclear leucocytes play an important role in the acute rejection of xenografts. The previously reported complement requirement for xenograft rejection was also confirmed in this work, by depleting the graft recipients of C3 with cobra venom factor.

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.

Bactericidal antibody response in the Pacific hagfish, Eptatretus stoutii

The hagfish, Eptatretus stoutii, has been shown to synthesize bactericidal antibodies after injections of gram-negative organisms. These bactericidins could be detected as early as 2 days after the primary injection. Secondary responses were accelerated, although titers were not significantly higher than those reached in the primary response. The bactericidins of hagfish were found to react with other gramnegative enteric bacteria, but not with gram-positive strains. The bactericidins show a lesser degree of specificity and a shorter induction period than other hagfish antibodies or most antibodies induced in higher vertebrates. The bactericidal activity was temperature dependent and could be irreversibly destroyed by heating at 50 C for 20 min. Immune sera were subjected to gel filtration on Sephadex G-200, and bactericidal activity was found to be associated with the excluded peak indicating a high-molecular-weight component. Evidence indicates that inducible immune responses of this bactericidal type represent a primitive capacity which arose before the emergence of vertebrate species.

Specific inactivation of the fourth complement component. I. In vivo studies

Intravascular injection of guinea pigs with the fourth complement component (C4) inactivator from shark serum resulted in severe serum C4 depletion that lasted for several hours. Active and direct passive Arthus reactions did not develop or were extremely mild in such C4 inactivator-treated animals as judged by gross and histological observation. In consideration of the specificity of the C4 inactivator, its independence of cofactors, and its failure to generate biologically active materials in the process of C4 inactivation, it is concluded that complement-dependent immune injury can be suppressed or avoided by interruption of the complement cascade at a single early step. The depression of the Arthus reaction beyond the time of C4 recovery prompted quantitative speculations concerning (i) the in vivo rate of C5a generation under conditions of limited C4 supply and (ii) the "saturation" of immune complexes. This view is supported by in vitro demonstration of functional inactivation or "saturation" of immune precipitates by repeated incubation with fresh guinea pig complement. It seems therefore conceivable that even temporary complement inactivation may have a profound beneficial effect on complement-dependent immune injuries.

Interaction of rheumatoid factor with infectious herpes simplex virus-antibody complexes

Rheumatoid factor, a human immunoglobulin of the IgM class, failed to attach to herpes simplex virus but did attach to infectious complexes composed of herpes simplex virus and antibody to herpes simplex virus. These newly formed complexes of infectious virus, antiviral antibody, and rheumatoid factor could be neutralized by complement or by antibody to human IgM. The ability of rheumatoid factor to enhance virus neutralization in the presence of complement represents a hitherto unrecognized biological role for rheumatoid factor.

The role of the sixth component of complement in the rejection of kidney xenografts

The time of rejection of dog kidney grafts in normal and in C6-deficient rabbits was not significantly different. It is concluded that the last four components of complement are not involved in this form of violent xenograft rejection. The requirement for the first components may be explained by polymorphonuclear leucocyte chemotaxis, since these cells were found in the glomeruli of rejected kidneys.

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.