Studies on the defect which causes absence of decay accelerating factor (DAF) from the peripheral blood cells of an individual with the Inab phenotype

1. We have studied the peripheral blood cells of an individual with the Inab phenotype who is deficient in decay accelerating factor (DAF). 2. In contrast with the situation in paroxysmal nocturnal haemoglobinuria, membranes from peripheral blood cells of the Inab phenotype individual lack DAF, but retain the other glycosylphosphatidylinositol-linked proteins acetylcholinesterase and LFA-3. 3. Unlike normal Epstein-Barr-virus-transformed lymphoblastoid cell lines (EBV-LCL), DAF was not expressed on EBV-LCL derived from peripheral blood lymphocytes of the Inab individual. 4. No differences in the DAF gene of normal and Inab phenotype individuals could be detected by Southern blotting studies. 5. EBV-LCL derived from the Inab individual had a gross reduction in the level of DAF mRNA compared with normal EBV-LCL. 6. Our results suggest that the DAF gene in the Inab phenotype contains a mutation which affects the transcription or processing of DAF mRNA.

Hypocomplementemic proliferative glomerulonephritis with C3 nephritic-factor-like activity in multiple myeloma

Advanced renal failure, nephrotic-range proteinuria due to proliferative glomerulonephritis and multiple myeloma with circulating IgG2 lambda and free lambda light-chain paraproteins occurred in a 31-year-old male. Commonly established causes of renal failure in multiple myeloma were excluded. Immunofluorescence revealed heavy granular glomerular deposition of C3. Serum C3 was decreased, and C3c was increased. C3 nephritic-factor (C3 NeF)-like activity was demonstrated in the serum. Plasmapheresis and chemotherapy resulted in a decrease in paraprotein concentration up to 90%, a decrease in C3 NeF-like activity to negligible, normal serum complement levels and a marked improvement in both renal function and proteinuria. With reference to the literature, the possibility of a syndrome of paraproteinemia, C3 NeF-like activity and glomerulonephritis is forwarded.

Anticomplementary activity in serum of women with a history of recurrent pregnancy loss

Viral complement fixation tests on women with a history of recurrent pregnancy loss were complicated by the presence of anticomplementary activity. This activity reflects the presence of a factor(s) in a patient's serum that nonspecifically fixes complement. When all patient sera tested were compared, 64.7% of women with recurrent pregnancy loss had anticomplementary activity compared with 22.0% among normal fertile pregnant women (p less than 0.01). In delineating when anticomplementary activity developed, it was found that 41.8% of women with recurrent pregnancy loss compared with 12.9% of normal pregnant women had this activity on entry to the study (p less than 0.01). This was primarily due to the fact that among women with recurrent pregnancy loss 50.0% of the pregnant versus 33.0% of the nonpregnant women had activity (NS). However, 55.2% of the anticomplementary negative women with recurrent pregnancy loss converted to a positive status compared with 15.4% of normal women (p less than 0.05). This was directly influenced by a conversion rate of 78.6% during pregnancy among women with recurrent pregnancy loss who entered the study nonpregnant and with no known cause for loss compared with a 33.3% conversion rate in their pregnant counterparts with recurrent pregnancy loss (p less than 0.025). Conversion to positive anticomplementary status occurred primarily by 20 weeks of gestation and appeared to be transient. Overall there was no association between the presence of anticomplementary activity and cervical colonization with genital mycoplasmas. The data suggest that women with a history of recurrent pregnancy loss develop a serum factor(s), usually by 20 weeks' gestation, that fixes complement. Thus these observations describe an additional anomaly in the immune system of women who experience recurrent pregnancy loss.

A reason for the cytolytic inefficiency of murine serum

Murine serum exhibits very poor haemolytic and bactericidal activity. We report that this is due, at least in part, to the presence of a potent, naturally occurring plasma inhibitor of the terminal complement sequence. The inhibitor is a heat-stable euglobulin. It is highly effective in suppressing haemolysis following complement activation on target erythrocytes with heterologous serum. It also inhibits C3-independent reactive haemolysis of guinea-pig erythrocytes with human C5b-9. Current evidence indicates that the inhibitory factor acts at the C5b-7 stage by preventing binding of the terminal complement complex to cells undergoing complement attack. In this respect, the inhibitor differs from the previously recognized regulators of the terminal complement sequence including plasma S-protein. The inhibitor does not protect C5b-7-laden cells from the action of C8 and C9, and also does not suppress formation of haemolytically inactive SC5b-9 in the fluid phase. The action of murine inhibitory factor is not confined to the red cell, and its presence can totally abolish the bactericidal activity of human serum on a sensitive, rough E. coli K12 strain.

Persistently circulating C3 nephritic factor (C3 NeF)-stabilized alternative pathway C3 convertase (C3 CoF) in serum of an 11-year-old girl with meningococcal septicemia--simultaneous occurrence with free C3 NeF

Hemolytic complement was found to be absent in the serum of an 11-yr-old girl (R.N.) with meningococcal septicemia. C1, C4, and C2 were slightly decreased, C3 was absent, C5-C9 within the normal range. B levels immunochemically and electrophoretic mobility of B were normal. C3d was greater than 1000% of a pooled EDTA-plasma standard indicating hypercatabolism of C3. On incubation of the patient's serum with normal human serum activation of C3 occurred even in the presence of 0.04 M EDTA. The amount of C3b generated was, however, greater without any chelating agent or in Mg-EGTA. On gel filtration of the serum two protein containing peaks were found to be responsible for activation of C3: the IgG containing peak was able to activate C3 in normal human serum without chelating agents and in Mg-EGTA but not in the presence of EDTA. The IgM-containing peak activated the third component of complement even in the presence of EDTA. The factor responsible for this phenomenon was termed C3 converting factor (C3 CoF). The IgG fraction of the patients serum caused activation of C3 in Mg-EGTA. However, in the presence of EDTA no activation of C3 could be induced even if physiological concentrations of the patients IgG were added to normal human EDTA-plasma. Thus the activity of the patient's IgG did not differ from typical C3 nephritic factor. The decay of C2 in EAC42 intermediates in the presence of the patient's IgG was uninfluenced indicating that it did not carry autoantibody activity against the classical pathway convertase C4b,2a, an activity recently termed NFc.(ABSTRACT TRUNCATED AT 250 WORDS)

A natural auto-inhibitory factor of the terminal complement pathway in serum of Ctenodactylus gondi

The serum of Ctenodactylus gondi, a Tunisian rodent, contains a unique inhibitor of the terminal complement pathway. The auto-inhibitor has been partially characterized as a heat-stable euglobulin that is slightly retarded on a DEAE-ion exchange column at pH 7 and elutes as a symmetrical peak on Sephacryl S-300 in the mol. wt region of approximately 200,000. The inhibitor acts by preventing attachment of cytolytic C5b-9 complexes to natural target cells. It does not appear to affect formation and function of C3-convertase, does not exert inhibitory effects at stages later than C5b-7 formation, and also does not prevent formation of SC5b-9 in serum. That the factor prevents attachment of C5b-7/C5b-9 to cells has been demonstrated in hemolysis model systems using sheep EA + human serum, and in the C3-independent reactive lysis system with the use of ELISA methods and quantitative assays with radioiodinated C8. Addition of partially purified inhibitory factor to human sera or to sera of other animal species abolishes the hemolytic activities of these sera. The inhibitory factor of Gondi serum is the first inhibitor of the terminal pathway which has been shown to be capable of preventing cytolysis of cells undergoing complement attack under physiological conditions. The presence of this factor is probably partially responsible for the remarkable susceptibility of C. gondi towards bacterial and parasitic infections.

C3 nephritic factor determination. A comparison between two methods

C3 nephritic factor (NEF), an IgG autoantibody to the alternative pathway C3 convertase, is usually measured by crossed immunoelectrophoresis (CI) but recently a reliable haemolytic assay (HA) was described by Rother (1982). This method is more specific than CI because it is negative in sera with immune complexes, SLE and sera incubated with IgG aggregates. The haemolytic assay is sensitive enough to detect NEF antibody in serum from patients with only slightly low C3 levels and NEF negatives by CI. The haemolytic assay is easy to perform and reproducible, the interassay coefficient of variation being 10.7% compared to 64% in the CI. The intra-assay coefficient of variation in CI was 28% compared to 5.5% in the haemolytic assay. The haemolytic method enabled us to study the kinetic effects of NEF on C3b.Bb bound to sheep erythrocytes, and the lysis mediated by ShE.C3b.Bb.NEF complex. Also the C and NEF binding to sheep erythrocytes was studied.

C3 nephritic factor in an individual with recurrent viral infection and lipodystrophy

A patient with nephritic factor in the serum following an attack of disseminated herpes is described. In the majority of cases, the factor is associated with mesangio-capillary glomerulonephritis, with or without partial lipodystrophy. It has, however, been described in cases of partial lipodystrophy alone, in one patient with recurrent pyogenic infections, and in one healthy individual. It has not previously been described in an individual with disseminated viral infection.

A new and specific enzyme-linked immunosorbent assay for the detection of C3 nephritic factor

C3 nephritic factor (C3 NeF) was measured by assessing its capacity to form complex with C3 and B using an enzyme-linked immunosorbent assay (ELISA). Incubation of C3 NeF with normal human serum in the presence of MgEGTA resulted in a dose-dependent increase of C3-B-IgG complex. No complex was formed in EDTA. The C3 NeF titer estimated in this way was in good accordance with those reported previously by other indirect methods.

Distribution of decay-accelerating factor in the peripheral blood of normal individuals and patients with paroxysmal nocturnal hemoglobinuria

Decay-accelerating factor (DAF) is a 70,000 Mr protein that has been isolated from the membrane of red cells. The function of DAF is to inhibit the assembly of amplifying enzymes of the complement cascade on the cell surface, thereby protecting them from damage by autologous complement. We raised monoclonal antibodies to DAF and used them to study its distribution in cells from the peripheral blood of normal individuals and of patients with paroxysmal nocturnal hemoglobinuria (PNH), a disease characterized by the unusual susceptibility of red cells to the hemolytic activity of complement. The results of immunoradiometric assays and of fluorescence-activated cell sorter analysis showed that DAF was present not only on red cells but was widely distributed on the surface membrane of platelets, neutrophils, monocytes, and B and T lymphocytes. By Western blotting, we observed small but consistent differences in the Mr of DAF from the membranes of various cell types. Quantitative studies showed that phagocytes and B lymphocytes, which presumably enter more frequently in contact with immune complexes and other potential activators of complement, had the highest DAF levels. As previously reported by others, the red cells from PNH patients were DAF deficient. When the patients' red cells were incubated in acidified serum (Ham test), only the DAF-deficient cells were lysed. In addition, we detected defects in DAF expression on platelets and all types of leukocytes. The observed patterns of DAF deficiency in these patients were consistent with the concept that the PNH cells were of monoclonal origin. In one patient, abnormal and normal cells were found only in the erythroid, myeloid, and megakaryocytic lineages. In two other patients, the lymphocytes were also DAF deficient, suggesting that a mutation occurred in a totipotent stem cell. It appears, therefore, that the lesion leading to PNH can occur at various stages in the differentiation of hematopoietic cells.

C3 nephritic factor in a patient with recurrent Neisseria meningitidis infections

A 15-year-old female experienced two systemic infections with N.meningitidis (group C and B) within a two months period. Classical as well as alternative pathway CH50 determinations on the patients serum showed no lysis. All individual complement factor concentrations, except for C3, were found to be within the reference area. Crossed immunoelectrophoretic analysis of C3 revealed no demonstrable native C3. The patient had normal levels of C3c and a markedly elevated C3d concentration. Serum from the patient was found to convert all native C3 in normal sera within 10 minutes at 37 degrees C. The active converting principle, present in the IgG fraction activated C3 in C4-depleted serum, and had a dose dependent stabilizing effect on the EA-C3bBb complex. The isolated factor showing the characteristics of C3 nephritic factor (C3 NeF), was unchanged in the patients serum over a ten months observation period. Circulating immune complexes (IC) could not be demonstrated by a C1q-dependent assay but the patients capacity to solubilize preformed IC in vitro was virtually abolished. The patient had no signs of renal disease or lipodystrophy.

Evidence for restriction of the ability of complement to lyse homologous erythrocytes

This research explored the possibility that a mechanism for the inhibition of C exists that is capable of restricting lysis of antibody-sensitized homologous E. The ability of C to lyse E from six species was compared by using a passive lysis system that employed E coated with B. abortus LPS and bovine antibodies specific for B. abortus. A system was developed that permitted comparisons of the hemolytic efficiencies of heterologous and homologous C target cell combinations. C from all of the species tested lysed heterologous E effectively, but homologous E were poorly lysed. Furthermore, a serum factor appeared to be involved with restriction of lysis of homologous E:LPS:Ab by heterologous C, and the restriction was specific for homologous E. Human E:LPS:Ab that were washed after incubation with CH were resistant to subsequent lysis by heterologous C. This restriction did not occur at 0 degrees C or in the absence of antibodies. Incubation of homologous C with EH:LPS:Ab resulted in consumption of C1, C2, C3, and C4, but not C5. The treated CH would lyse sheep EAC1423, but it would not lyse sheep EA, EACI, or EAC142. Late reacting C components (C5 through C9) were not detectable on EH:LPS:Ab after incubation with CH, but C4 and C3 were bound to the cells. Rat late-reacting C components (rat C-EDTA) were capable of detecting C3 convertase sites on EH:LPS:Ab that had been reacted with CH. However, homologous late-reacting components and guinea pig late-reacting components were unable to detect the C3 convertase sites.

C3 nephritic factor and hypocomplementaemia in a clinically healthy individual

Nephritic factor was detected in an individual whose serum showed a selective decrease in the third component of complement (C3) during and subsequent to an illness resembling disseminated gonococcal infection (DGI). As is characteristic of C3 nephritic factor (C3NeF), its activity was heat stable, was associated with IgG, and enhanced cleavage of normal human serum C3 via the alternative pathway. However, unlike previously reported cases of C3NeF detection in association with glomerulonephritis and/or lipodystrophy, this patient has had no significant disease before or more than 2 years after the apparent DGI. The significance of C3NeF in a healthy individual is unexplained, but this study suggests its occurrence may be more ubiquitous than previously suspected.

Effect of dehydroepiandrosterone on hereditary angioedema

Hereditary angioneurotic edema (HAE) is a complement-related clinical disorder with a deficiency of the C1 esterase inhibitor protein. Eight patients with severe attacks of the disease were treated with the adrenal "androgen" dehydroepiandrosterone sulphate (DS). Steroid therapy for 3-28 months resulted in dramatic improvement in their clinical state and a moderate increase in the serum concentration of C1 inhibitor. There was a significant increase in the serum level of either unconjugated dehydroepiandrosterone (D) or of DS during treatment.

Meningococcal meningitis associated with persistent hypocomplementaemia due to circulating C3 nephritic factor

Two teenage patients who presented with meningococcal meningitis were found to have persistently low C3 levels even after recovery. This was accompanied by circulating C3 nephritic factor, which persisted for more than 12 months in each case. Neither patient had evidence of partial lipodystrophy or of glomerulonephritis initially, although one patient subsequently developed mesangioproliferative glomerulonephritis following a second admission with pneumococcal pneumonia. It is possible that the generation of the nephritic factor was initiated during the presenting illness.

Biological significance of the C3 nephritic factor in membranoproliferative glomerulonephritis

Serum levels of the C3 nephritic factor (C3NeF), an IgG autoantibody directed against the C3bBb convertase of the alternative complement pathway, and of eight complement components (C1q, C4, C3, C3d, C5, C9, fB and properdin) were measured in 109 serum samples from 27 patients with idiopathic membranoproliferative glomerulonephritis (MPGN) (type I, 20 cases, and type II, 7 cases) and 14 patients with secondary MPGN. Correlations between the concentrations of C3NeF, serum complement levels and progression of the renal damage were studied during the course of the disease in 14 patients with C3NeF activity. The results showed that (1) C3NeF activity was more frequent in patients with type II MPGN than in patients with type I disease; nevertheless there was a high incidence of this splitting activity in patients with secondary MPGN, (2) high levels of the complement components were present in patients with MPGN, (3) low levels of C3 occurred frequently in type II disease and in secondary MPGN, (4) there was no correlation between C3, fB and C3NeF levels, (5) the presence of C3NeF was associated with a more rapid deterioration of renal function. Longitudinal studies showed that serum levels of C3NeF were not satisfactory for monitoring the clinical course of the illness and, in this respect, are similar to the levels of other autoantibodies in patients with autoimmune disease. As MPGN is a clinical syndrome with various pathogeneses, we suggest that the autoantibody, C3NeF, should be considered only as a marker of some forms of MPGN.

C1 inhibitor deficiency simulating systemic lupus erythematosus

A 48-year-old Japanese woman with systemic lupus erythematosus-like lesions of the skin and lips was found to have hereditary angio-oedema. Complement studies revealed low CH50, C1q, C4 and C1 inhibitor levels, with normal C3 and C5 levels. Dramatic clinical improvement followed fresh normal human blood transfusion and systemic betamethasone administration, while the deficient complement component levels were unchanged.

Characterization of a C3/C3b regulatory protein in normal human serum

A protein which alters the activity of C3 and C3b has been isolated from normal human serum by sequential column chromatography. In purified form, at normal serum concentration, this protein fixes to cell-bound C3b. It cannot bind to C3d. After fixation, it prevents the inactivation of C3b by beta 1H and C3bINA in both the classical and alternative pathway C5 convertases. Independent of this action, fixation to C3b also markedly enhances the subsequent activity of C5. At higher concentrations, however, this protein is capable of blocking the activation of C3 by both pathway C3 convertases. This material, therefore, appears to represent a potent means of regulating several critical aspects of the biologic activity of the complement system.

Studies on the nature of heat-labile anti-complementary activity in normal human serum

Heat-labile anti-complementary activity (ACA) appears in normal human serum during storage or heating as endogenous haemolytic activity disappears. Following gel filtration of unheated serum, two peaks of heat-labile ACA are present. The ACA of both whole and fractionated serum has previously been attributed to the presence of heat-labile immunoglobulin aggregates or immune complexes. Our data demonstrate that the heavy peak of ACA obtained by gel filtration does not bind to 125I-C1q or to Raji cells, and that its effect is abolished to C1INH, suggesting that it represents C1 rather than immunoglobulin aggregates or immune complexes. The lighter peak of ACA in fractionated serum has the functional characteristics of C1s and free C1s is demonstrable in fractions containing this activity. The ACA of whole serum likewise has functional characteristics of C1. The anti-complementary effect of C1 on guinea-pig complement would not be evident in the complement fixation assay until most endogenous haemolytic activity in human serum has been inactivated, either by heat or by storage. C1INH only partially inhibits this ACA in serum or in solutions containing isolated C1 in high concentrations. These observations indicate that heat-labile ACA in whole or fractionated sera is due to the presence of C1 and C1s and that this activity cannot be taken as evidence for the presence of immune complexes.

Inhibition of proteases in coagulation, kinin-forming and complement systems by alpha2-plasmin inhibitor

Inhibitory activities of alpha2-plasmin inhibitor against various proteases were investigated. The inhibitor promptly inhibited the esterolytic activity of alpha-chymotrypsin and progressively inhibited the esterolytic or amidolytic activities of bovine plasma kallikrein, bovine thrombin and bovine activated factor X. Heparin had no effect on the reaction of the inhibitor with thrombin or activated factor X. However, the inhibitor had no effect on the activities of human C-1-esterase, papain and snake venom kininogenase. On the basis of its rapid inhibition of kallikrein, alpha2-plasmin inhibitor is considered to exert some regulating effect on kallikrein activity in plasma.