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PubMed1988

Complements in diabetes mellitus: activation of complement system evidenced by C3d elevation in IDDM.

To characterize insulin-dependent diabetes mellitus (IDDM) and non-insulin-dependent diabetes mellitus (NIDDM) in terms of the complement system, some components of the system as well as the related substances and indices were studied. CH50, C3, C4 and C3bINA significantly increased in both IDDM and NIDDM compared with non-diabetic healthy controls. ACH50 was also elevated in NIDDM, whereas it was similar in IDDM and controls. Besides, the serum concentration of C3d, a breakdown product of C3, was higher in IDDM than in NIDDM and healthy controls, but that in NIDDM did not differ significantly from the control. B1Hg1 was not different among IDDM, NIDDM and non-diabetic controls. These observations suggested that there is a high level of complements in both types of diabetes mellitus, but the complement activation seems to be much enhanced in IDDM compared with NIDDM.

Complement Activation↗
PubMed1987

Formation of the membrane attack complex of complement (MAC) on erythrocytes from monocyte-produced terminal complement components.

By using antibodies against C5, C6, C7, C8, and C9, we found that terminal complement components were deposited on IgM-coated sheep erythrocytes (EIgM) kept in serum-free endotoxin-stimulated monocyte cultures for 24 or 48 h. Monoclonal antibodies revealed C9 neoantigens on the EIgM. There was no specific binding of an anti-S protein antibody, which reacts with the SC5b-9 complex, to the EIgM. Controls were native sheep erythrocytes (E) treated similarly which, in contrast to EIgM, do not activate the classical pathway of complement. Cycloheximide (1.0 microgram/ml) in the cell cultures resulted in no specific binding of the anti-C9 antibodies to EIgM. A fraction of the EIgM was lysed during incubation with the monocytes. We conclude that the monocytes secrete C5, C6, C7, C8, and C9, which form the membrane attack complex of complement (C5b-9) on the EIgM.

Animals↗
PubMed1990

Protection of human amniotic epithelial cells (HAEC) from complement-mediated lysis: expression on the cells of three complement inhibitory membrane proteins.

Cultured human amniotic epithelial cells (HAEC) were found by immunofluorescence microscopy to express three complement inhibitory membrane proteins, CD59 antigen, decay-accelerating factor (DAF) and membrane attack complex (MAC) inhibitory protein (MIP), on their surfaces. The effects of incubation with Fab2 fragments of monoclonal antibodies (mAb) raised against these proteins on susceptibility of sensitized cells to lysis by homologous complement was examined. Percentage cell lysis was markedly increased in the presence of Fab2 anti-CD59 and to a lesser, but significant, extent in the presence of Fab2 anti-DAF. Fab2 anti-MIP did not alter the sensitivity of the cells to lysis by complement.

Amnion↗
PubMed1976

Lysis of tumor cells by antibody and complement. VII. Complement-dependent 86Rb release--a nonlethal event?

The guinea pig hepatoma (line-1) treated with anti-Forssman antibody (TA) and GPC sequentially released 86Rb, 14C from 14C aminoidobutyric acid and failed to exclude trypan blue. Incubation of TA with fluid phase GPC for 1 min caused maximal 86Rb release; however, if the GPC was removed at this time, the cells were not subsequently killed. Using a number of naturally occurring human sera deficient in a complement component we have shown 86Rb release requires the binding of the complement components 1 through 8, but there was no absolute requirement for C9. Irreversible damage to the cell as measured by 14C AIB release or uptake of trypan blue required the complete sequence of complete sequence of complement components. These observations indicate that 86Rb release is not a relible indicator cytotoxicity.

Animals↗
PubMed1991

Intersection of the complement and immune systems: a signal transduction complex of the B lymphocyte-containing complement receptor type 2 and CD19.

The complement system augments the humoral immune response, possibly by a mechanism that involves the B lymphocyte membrane receptor, CR2, which binds the C3dg fragment of C3 and triggers several B cell responses in vitro. The present study demonstrates that CR2 associates with a complex of membrane proteins that may mediate signal transduction by ligated CR2. Monoclonal antibodies to CR2 immunoprecipitated from digitonin lysates of Raji B lymphoblastoid cells a membrane complex containing CR2, approximately equimolar amounts of CD19, which is a member of the immunoglobulin superfamily, and three unidentified components: p130, p50, and p20. The complex, which was immunoprecipitated also with anti-CD19, could be dissociated by Nonidet P-40, accounting for its absence in previous studies of CR2. Expression of recombinant CR2 and CD19 in K562 erythroleukemia cells led to formation of a complex that contained not only these two proteins but also p130, p50, and p20, and another component, p14. These unidentified components of the CR2/CD19 complex coimmunoprecipitated with CD19 and not with CR2 from singly transfected cells, indicating primary association with the former. CD19 replicated the capacity of CR2 to interact synergistically with mIgM for increasing free intracellular Ca2+, suggesting that the complex mediates this function of CR2. Therefore, CR2 associates directly with CD19 to become a ligand-binding subunit of a pre-existing signal transduction complex of the B cell that may be representative of a family of membrane protein complexes. This interaction between the complement and immune systems differs from that between immunoglobulin and Clq by involving membrane rather than plasma proteins, and by having complement involved in the afferent phase of the immune response.

Antigens, CD↗
PubMed1989

The IgG subclass pattern of complement activation depends on epitope density and antibody and complement concentration.

Using a matched series of human-mouse chimaeric IgG anti-5-iodo-4-hydroxy-3-nitrophenacetyl (anti-NIP) antibodies and NIP-bovine serum albumin (NIP-BSA) we examined how different variables influence the activation pattern of complement. When BSA was used with different hapten densities and the input of NIP-BSA was altered, we observed a change in the subclass reaction pattern. IgG3 fixed more Clq than IgG1 and IgG2 in all situations. IgG1 was slightly better than IgG3 and IgG2 at high antigen concentrations at activating C4 and C3 and inducing formation of the terminal complement complex (TCC). When the epitope density and/or the NIP-BSA concentration was reduced, IgG3 became best, followed by IgG1 and IgG2. IgG1 now revealed a marked prozone. Furthermore, IgG4 was found to activate C3 and mediate TCC formation at high epitope and complement concentrations.

Antibodies↗
PubMed1989

Assessment of the activation pathways of the complement in psoriatic patients by use of complement fragment C4d and Bb measurements.

We have measured the complement fragment C4d and Bb levels in the plasma of 51 psoriatic patients and 54 normal controls. The C4d and Bb levels were not significantly elevated in the plasma of the psoriatic patients when compared with those of controls, except in patients with more than 60% skin involvement who exhibited an increase in Bb levels. C4d levels, however, did decrease slightly after successful treatment of psoriasis. Although these results suggest that the C4d and Bb levels partly reflect the complement activation in vivo, they do not seem to be suitable parameters to clarify the mechanism of complement activation in psoriasis.

Adolescent↗
PubMed1977

Measurement of hemolytic complement and the third component of complement in nonhuman primates.

Complement, determined by hemolytic assay, and the third component of complement (C3), determined by radial immunodiffusion assay, were measured in nine nonhuman primate species. The species studied were the titi (Callicebus mollach). The sooty mangabey (Cercocebus atys), the thick-tailed galago or bushbaby (Galago crassicaudatus panganiensis), the crab-eating monkey (Macaca fascicularis), the rhesus monkey (Macaca mulatta), the bonnet monkey (Macaca radiata), the stumptailed macaque (Macaca speciosa), the yellow baboon (Papio cynocephalus), and the black-and-red tamarin (Saguinus nigricollis). Both sheep and bovine erythrocytes were used in the hemolytic complement assays. With the sheep erythrocyte system, sera from four species (yellow baboon, sooty mangabey, bonnet monkey, black-and-red tamarin) had similar titers with both antibody sensitized and non-sensitized erythrocytes. In contrast, the titers obtained using sensitized bovine erythrocytes was always higher than the values obtained using non-sensitized bovine erythrocytes. In all species, the titers for non-sensitized sheep erythrocytes was higher than the titer for non-sensitized bovine erythrocytes. When the species were compared for cross reactivity using the radial immunodiffusion assay for human C3, the rhesus monkey showed the strongest cross reaction; the thick-tailed galago, a prosimian, showed no detectable cross reactivity; and the other species examined showed intermediate degrees of reactivity.

Animals↗
PubMed1977

The cold activation of the classical complement pathway: The cause of the differences between plasma and serum complement in liver cirrhosis.

The mechanism responsible for making the differences between plasma and serum complement (CH50) was studied on eight patients with hepatitis-B(s) antigen negative alcoholic liver cirrhosis. CH50 and C4 activities of the sera of all patients were equal to those of the corresponding EDTA-plasma, when sera wre separated after clotting the blood at 37 degrees C. CH50 and C4 activities of the sera, prepared at 21 degrees C or 4 degrees C, from four of eight patients were very low. When serum from one of these four patients was added to normal human serum, C4 activity of the serum mixture markedly decreased at 4 degrees C but not at 37 degrees C. The inactivation of C4 was prevented by adding EDTA or heparin to the serum mixture. These results indicated that very low complement in the sera, prepared at 21 degrees C or 4 degrees C, of the four cases were due to the cold activation of the classical complement pathway.

Cold Temperature↗
PubMed1991

A flow cytometric assay for measuring complement receptor 1 (CR1) and the complement fragments C3d and C4d on erythrocytes.

A flow cytometric assay (FCA) was developed to measure complement receptor 1 (CR1) and the complement fragments C3d and C4d on erythrocytes. It was possible to measure these parameters accurately with intra- and interassay coefficients of variation of 2.0% and 6.5% respectively. The method was able to discriminate between low and high levels of erythrocyte CR1, C3d and C4d. Comparison with a previously described RIA method gave excellent correlation coefficients with r2 values of 0.94, 0.93 and 0.91 for CR1, C3d and C4d respectively. The flow cytometric assay was used to measure CR1, C3d and C4d on the erythrocytes of 98 healthy individuals and the 95% upper limits for C3d and C4d were established. There was a wide distribution of CR1 levels amongst these individuals but their C3d and C4d levels were low and often not above background. The possible application of this method in clinical medicine is discussed.

Antigens, CD↗
PubMed1988

The cytolytic C5b-9 complement complex: feedback inhibition of complement activation.

We describe a regulatory function of the terminal cytolytic C5b-9 complex [C5b-9(m)] of human complement. Purified C5b-9(m) complexes isolated from target membranes, whether in solution or bound to liposomes, inhibited lysis of sensitized sheep erythrocytes by whole human serum in a dose-dependent manner. C9 was not required for the inhibitory function since C5b-7 and C5b-8 complexes isolated from membranes were also effective. No effect was found with the cytolytically inactive, fluid-phase SC5b-9 complex. However, tryptic modification of SC5b-9 conferred an inhibitory capacity to the complex, due probably to partial removal of the S protein. Experiments using purified components demonstrated that C5b-9(m) exerts a regulatory effect on the formation of the classical- and alternative-pathway C3 convertases and on the utilization of C5 by cell-bound C5 convertases. C5b-9(m) complexes were unable to inhibit the lysis of cells bearing C5b-7(m) by C8 and C9. Addition of C5b-9(m) to whole human serum abolished its bactericidal effect on the serum-sensitive Escherichia coli K-12 strain W 3110 and suppressed its hemolytic function on antibody-sensitized, autologous erythrocytes. Feedback inhibition by C5b-9(m) represents a biologically relevant mechanism through which complement may autoregulate its effector functions.

Complement Activation↗
PubMed1988

A physical map of the human regulator of complement activation gene cluster linking the complement genes CR1, CR2, DAF, and C4BP.

We report the organization of the human genes encoding the complement components C4-binding protein (C4BP), C3b/C4b receptor (CR1), decay accelerating factor (DAF), and C3dg receptor (CR2) within the regulator of complement activation (RCA) gene cluster. Using pulsed field gel electrophoresis analysis these genes have been physically linked and aligned as CR1-CR2-DAF-C4BP in an 800-kb DNA segment. The very tight linkage between the CR1 and the C4BP loci, contrasted with the relative long DNA distance between these genes, suggests the existence of mechanisms interfering with recombination within the RCA gene cluster.

CD55 Antigens↗
PubMed1975

Complement-mediated bactericidal system: evidence for a new pathway of complement action.

The early components of human complement (C1, C4, and C2) plus certain serum euglobulins will kill pathogenic strains of Shigella sonnei. Serum from patients with hereditary C3 deficiencies and specific antiserums to C3, C5, and C6 were utilized to demonstrate the absence of requirements for late-acting complement components in this unusual bactericidal system.

Antibodies, Bacterial↗
PubMed1985

C56 formation in the reaction mixture of isolated complement components through the classical complement pathway.

The mechanism of hemolysis of unsensitized erythrocytes by a mixture of 9 isolated, human-derived complement components, C1s, C4, C2, C3, C5, C6, C7, C8 and C9 (C1s-C9) was studied. Of the tested erythrocytes, guinea pig erythrocytes (Egp) were the most susceptible to lysis by C1s-C9, followed by human and sheep erythrocytes. Contamination of the isolated complement components by C56 was ruled out. It was determined that a factor was generated in the reaction mixture of C1s, C4, C2, C3, C5 and C6 (C1s-C6), which had lytic activity against Egp when C7, C8 and C9 were added. We found that the lytic factor was similar to C56 in the following properties: (1) the activity of the lytic factor decreased when incubated with isolated C7 prior to its reaction with Egp; (2) the lytic factor did not bind to Egp by itself but it did bind in the presence of C7; (3) EDTA did not have any inhibitory effect on the lytic factor; (4) the activity of the lytic factor decreased by treatment with anti-C5 and anti-C6 but not by treatment with anti-C3 and anti-C4, and (5) gel filtration of the reaction mixture (C1s-C6) indicated that the elution volumes of the lytic factor and of isolated C56 were similar. Thus, it is likely that C56 is generated in the reaction mixture of C1s-C6 and the lytic factor binds to unsensitized erythrocytes together with C7, to form an intermediate EC567 which is susceptible to lysis by the action of C8 and C9.

Animals↗
PubMed1989

Molecular cloning and characterization of the novel, human complement-associated protein, SP-40,40: a link between the complement and reproductive systems.

The cDNA sequence encoding the human complement-associated protein, SP-40,40, is reported. The two chains of SP-40,40 are coded in a single open reading frame on the same mRNA molecule, indicating the existence of a biosynthetic precursor protein which matures post-synthetically by the proteolysis of at least one peptide bond. The precursor is preceded by a signal sequence for vectorial export and contains six N-linked glycosylation sites distributed equally between the two chains of the structure. The sequence of the SP-40,40 precursor bears a 77% identity to a rat sulphated glycoprotein-2 (SGP-2) which is the major secreted product of Sertoli cells. The presence of SP-40,40 within human seminal plasma at levels comparable to those in serum was demonstrated, indicating that SP-40,40 and SGP-2 are serum and seminal forms of the same protein. A sequence of 23 amino acids within the beta-chain of SP-40,40 exhibited significant homology to corresponding segments located within complement components C7, C8 and C9. The short cysteine-containing motif represented the only evidence of a possible vestigial relationship between SP-40,40 and other complement components. The precise role of SP-40,40 is not known in either blood or semen but the present findings document an intriguing link between the immune and the reproductive systems.

Amino Acid Sequence↗
PubMed1988

Complement-mediated cytolytic activity associated with cytomegalovirus complement-fixing IgM antibody.

Cytomegalovirus-specific complement-fixing IgM (CMV CF-IgM) antibody was detected in 12/84 (14.3 percent) sera containing CMV-specific IgM. Higher titres were obtained by using a purified antigen preparation containing enveloped virus particles and membrane fragments when compared with a crude extract of infected cells, suggesting that the CF component of CMV IgM reacts predominantly with antigens on the surface of the infected cells. This also accounts for its complement-mediated cytolytic activity. Neither CMV-specific non-complement-fixing IgM nor CMV-specific IgG demonstrates cytolytic activity.

Antibodies, Viral↗
PubMed1989

Lack of complementation between xeroderma pigmentosum complementation groups D and H.

The construction of permanent hybrid cell lines between xeroderma pigmentosum (XP) cells from different complementation groups allows analysis not only of the degree of repair correction but also of the restoration of biological activity to the UV-irradiated cells. With use of an immortal human cell line (HD2) that expresses excision repair defects typical of XP group D, a series of permanent hybrid cells has been produced with XP cells from groups A to H. Excision repair, as measured by incision analysis and unscheduled DNA synthesis, is restored to normal or near normal levels in crosses involving HD2 and cells from XP groups A, B, C, E, F, G, and I. All these hybrids show complementation for the recovery of normal UV resistance. As expected, hybrids expressing poor incision and hypersensitivity to UV were produced in crosses between HD2 and XPD fibroblasts, but they were also produced without exception when XPH was the partner. In the permanent HD2 x XPD or XPH hybrids, analysis of incision capacity reveals abnormally low activity and therefore that there has been no complementation. The true hybrid nature of HD2 x XPH cells has been confirmed by HL-A and -B tissue typing; moreover, detailed kinetic analysis of incision in these cells shows that the XPH phenotype, rather than the XPD, is expressed, i.e. breaks accumulate at low UV fluence of 1 J/m2. To help confirm these findings, another immortal XPD cell line was used in fusions involving HD2, XPH, or XPI. Cells resistant to ultraviolet were produced only with XPI fibroblasts. These data are discussed in terms of whether XPD and H mutations are likely to be allelic with respect to incision.

DNA Damage↗