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

Interactions of the complement system with endotoxic lipopolysaccharide: consumption of each of the six terminal complement components

Large amounts of each C'3, C'5, C'6, C'7, C'8, and C'9 were consumed when guinea pig serum was incubated with endotoxic lipopolysaccharide, zymosan, or preformed immune complexes. Since these C' components subserve several of the biological activities which follow the injection of endotoxins into experimental animals, these experiments support the hypothesis that certain biological effects induced by endotoxins may be mediated via the C' system, and may account for some of the known similarity in the reactivities evoked by endotoxins and immune complexes in vivo.

The second component of human complement: its isolation, fragmentation by C'1 esterase, and incorporation into C'3 convertase

A method has been described for the purification and isolation of the second component of complement (C'2) from human serum. The protein is a beta(1)-globulin with an approximate molecular weight of 117,000. Immunochemical analysis using a variety of specific antisera, including a monospecific antiserum to the isolated protein, indicate that the C'2 protein represents a heretofore unrecognized human serum constituent. Isolated C'2 contained 2 x 10(9) "effective molecules" per microgram and 1000 hemolytically active C'2 molecules were required to produce a single hemolytically effective C'2 site on erythrocytes undergoing immune cytolysis. C'1 esterase treatment of C'2 resulted in reduction of both its electrophoretic mobility and its molecular size, the latter observation indicating fragmentation of the molecule. Direct evidence was presented for the physical presence of C'2 as an integral part of the enzyme C'3 convertase.

Lupus nephritis: varying complement-fixing properties of immunoglobulin G antibodies to antigens of cell nuclei

Relative complement-fixing activity of antibodies to nuclear antigens, including DNA, were determined in serums of 15 patients with, and 65 patients without, active lupus nephritis, by comparing titers obtained in two methods. High complement-fixing activity of antibody was found in the nephritis group and low activity in the others. Results with immunoglobulin G fractions were similar.

Interactions of the complement system with endotoxic lipopolysaccharide. Generation of a factor chemotactic for polymorphonuclear leukocytes

Endotoxic lipopolysaccharide has recently been shown to fix large amounts of the complement components related to the biologic activities mediated by that system. The present study sought to determine whether the generation of chemotactic factor by endotoxin in serum was dependent upon complement system activation. Preheating serum, incubating at 0 degrees C, or incubating in the presence of EDTA, all prevented chemotactic factor generation as well as complement fixation by endotoxin. "Endotoxoids" deficient in complement-firing activity were also deficient in chemotactic factor generation. Chemotactic factor could not be generated by endotoxin in sera of mice congenitally deficient in the C'S component of complement, while chemotactic factor was generated by endotoxin in the sera of coisogenic mice with normal complement levels for that species. The chemotactic factor induced by endotoxin was heat stable and nondialyzable. Molecular sieve chromatography and sucrose density gradient ultracentrifugation demonstrated that the chemotactic factor was a relatively low molecular weight product (15,000-30,000) and as such different from previously scribed C' system-derived chemotactic factors. These experiments demonstrate that generation of chemotactic factor by endotoxin in serum is dependent upon C' system activation involving at least C'5. Furthermore, the relatively low molecular weight of this factor suggests that it might be derived from activation of a single complement component rather than from complexing of multiple complement components.

Interactions of the complement system with native and chemically modified endotoxins

Endotoxic lipopolysaccharides (LPS) isolated from Serratia marcescens, Veillonella alcalescens, and Salmonella typhosa were potent in their ability to induce fixation of complement (C') in normal guinea pig, rabbit, mouse, and human serum. The C'-fixing ability of LPS was pronounced even when assays were performed in undiluted serum, and was lost after each of four chemical modifications which resulted in loss of biological toxicities. The detoxification procedures had in common the cleavage of ester-bound, long-chain carboxylic acids. The ability of biologically active LPS to fix C' in normal guinea pig serum was reflected chiefly in dramatic uptake of classical C'3 (C'3t); fixation of C'1, C'4, and C'2 was virtually undetectable. Hence, it was the capacity for fixation of C'3t which was lost most overtly during detoxification. Addition of immune serum to the assay mixtures resulted in detectable fixation of C'1 and C'4. Biologically active LPS also fixed more of these components than did detoxified LPS. Immune serum restored the ability of detoxified LPS to fix C'3t, but whether this is by the original pathway is not yet clear. We concluded that the loss of certain biological activities and the loss of ability to fix C'3t in normal serum after LPS detoxification involved loss or rearrangement of substrates on LPS which either initiated or supported, or both, its interaction with the complement system. It was apparent that the ability to fix C' can serve as a valuable in vitro indicator of the integrity of the toxic conformation of biologically active LPS membrane fragments. These experiments supported the hypothesis that certain of the biological activities induced by endotoxins are mediated via the complement system.

Guinea pig complement: two active forms of first component

By solubility chromatography at pH 7.5 and low ionic strength, a partially purified preparation of the first component of guinea pig complement was separated into two fractions of different solubility under these conditions. On rechromatography, each fraction emerged in the same position as it had originally.

Nature of hamster complement-fixing antibody to adenovirus 12 tumor antigen

The presence of complement-fixing (CF) antibody reactive with T antigen and with viral C antigen in hamsters bearing adenovirus 12-induced tumors has been confirmed. Antibody activity in serum obtained at a time when the host was bearing large tumors was found to be associated exclusively with 7S immunoglobulins. Two populations of 7S immunoglobulins showing CF reactivity were distinguished by electrical charge, as determined by diethylaminoethyl cellulose chromatography and immunoelectrophoresis. No antibodies of the 19S IgM type were detected in the serum of hamsters bearing large tumors.

Interactions of the complement system with the surface and endotoxic lipopolysaccharide of Veillonella alcalescens

Electron microscopic studies demonstrated that lesions were produced on the endotoxic lipopolysaccharide (LPS) as well as on the cell surface of V. alcalescens after reaction with fresh guinea pig serum. These lesions were approximately 90 A in diameter, and were seen on two characteristic structural entities derived from LPS preparations after incubation with serum. The use of numerous inhibitors, inactivators, and reaction conditions affecting hemolytic C' activity revealed that these lesions were mediated by the C' system. Concomitant with lesion formation, C' was fixed; the effect on classical C'3 activity was pronounced. It is concluded that endotoxic LPS, as contained in the outer three-layered membrane of the bacterial cell, is a substrate for the C' enzymes. It is suggested that certain biological activities of endotoxin may derive from its effects on the C' system.

Anaphylatoxin in its relation to the complement system

The fifth component of complement that reacts hemolytically in the guinea pig or rat complement system, C'3b, is intimately associated with the generation of anaphylatoxin. Anaphylatoxin was formed (i) if this purified component reacted with a washed, intermediate complex consisting of antigen, antibody, and the first four components of complement; (ii) if the component was treated with trypsin; or (iii) if the component was incubated with a material isolated from cobra venom together with a fraction from serum other than complement. The significance of this fifth component as anaphylatoxinogen is discussed, and a common mechanism is proposed for the generation of anaphylatoxin in whole serum.

Deficiency of the sixth component of complement in rabbits with an inherited complement defect

A strain of rabbits with an inherited complement deficiency was shown to lack the sixth component of the hemolytic complement system. A method was elaborated for the partial purification of this component from normal rabbit serum. Upon injection of partially purified rabbit C'6 into C'6-deficient animals, an antibody was obtained which specifically inhibited the hemolytic activity of C'6. The data suggest that C'6-deficient serum either lacks the C'6 molecule or contains it in a chemically modified and inactive form.