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PubMed1976

A family with partial and total deficiency of complement C3.

A young White girl was found to have no detectable complement C3 or C1q. She suffered repeated attacks of pneumococcal meningitis and pneumococcal pneumonia. Her parents, and some of her siblings, had half the normal level of C3; other siblings were normal. She also had decreased IgG levels and increased IgM concentrations. These findings are correlated with a dysmorphic state of the germinal centres of the peripheral lymphoid tissues, seen after death.

Child↗
PubMed1992

[Complement C3 and C4 levels in serum from acute viral hepatitis].

Serial measurements of C3 and C4 complement components were performed in 50 patients with acute, uncomplicated viral hepatitis, in the beginning of the symptoms and in the peaks of serum transaminases. There were 17 patients diagnosed as having Hepatitis A virus (HAV) infection and 33 patients diagnosed as having Hepatitis B virus (HBV) infection. There were 4 women and 46 men with a mean age of 22.1 years. In the sera of 50 healthy control subjects serum C3 and C4 complement components measured, this group was composed of 15 women and 35 men with a mean age of 26 years. The complement component levels were observed to be reduced in both viral infections, where the reduction in C3 serum concentration was found to be statistically significant but reduction in C4 serum concentration was not.

Acute Disease↗
PubMed1979

Complement (C3), nutrition, and infection.

Complement (C(3)) was determined and related to various parameters of nutritional status and past infectious disease experience in a group of 53 rural preschool children in North India. Mean complement level was 25% lower than in an age-matched European reference population. Low complement (C(3)) levels were associated mainly with children who were both stunted and wasted, as well as with those who had experienced frequent purulent skin infections in the past.

Child, Preschool↗
PubMed1976

Complement C3 in serum and plasma, as measured by radial immunodiffusion with four commercial kits.

Quantitation of the C3 component of complement by single radial immunodiffusion is subject to error because the C3 molecule has several antigenic determinants and anti-C3 sera differ in their specificity to these determinants. C3 was measured in plasma (ethylenediaminetetraacetate anticoagulant) and serum, in five normal individuals, by use of four such commercial kits. The effects of ethylenediaminetetraacetate and of incubation at -20, 4, and 37 degrees C for 1, 2, and 7 days were investigated. We found wide variations in C3 in the same sample, as measured with different kits. Incubation for longer than 48 h at 4 degrees C changed C3 concentrations as compared to those in fresh samples. Reference sera for C3 assay and standardized procedures for sample processing are both essential to valid results.

Adult↗
PubMed1975

Third component of complement (C3): structural properties in relation to functions.

The third component of complement (C3) fulfills a pivotal role in the functions of the complement system. We have investigated the topological relationships among its polypeptide chains, physiologic fragments, enzyme attack regions, and functional sites. C3 consists of two chains (alpha and beta) which are linked by disulfide bonds and noncovalent forces and which have molecular weights of, respectively, 120,000 and 75,000. C3 is activated by action of C3 convertase on the alpha-chain. With hydrolysis of one polypeptide bonds, C3a, the 9000 dalton activation peptide is dislocated from the NH2-terminal portion of the alpha-chain. A previously concealed binding region is thereby transiently revealed in the C3b-fragment (181,000 dalton) which displays affinity for apparently nonspecific acceptors present on biological membranes. Binding of nascent C3b membranes occurs through the C3d portion of the fragment because subsequent action of the C3b-inactivator or trypsin on bound C3b causes release of C3c, but not of C3d. Bound C3b and C3d possess stable sites that are capable of binding to specific receptors present on a limited variety of cells. We propose that all known physiologically occurring fragments of C3 arise by enzymatic cleavage of the alpha-chain: C3a, C3b, C3c, and C3d. Whereas C3a (alpha1) and C3e (alpha2) consist of a single chain and C3b consists of two chains (alpha' and beta), C3c is composed of the entire beta-chain and multiple fragments of the alpha-chain, each of which is linked by disulfide bonds to the beta-chain.

Binding Sites↗
PubMed1986

Intercellular complement C3 binding in normal skin of patients without pemphigus.

We report here direct immunofluorescence studies of normal skin biopsies that exhibited only complement C3 staining in intercellular areas of epithelium with a view toward evaluating the significance of such findings. During a 5-year period, 11,000 skin biopsy specimens were examined for in vivo binding of immunoglobulins, fibrin, and complement C3 by means of defined direct immunofluorescence methods. Four of ten patients demonstrating intercellular C3 deposits alone had drug-related reactions or erythema multiforme, and four were subsequently shown to have a connective tissue disease. Pemphigus was ruled out in all ten cases in these retrospective studies. These observations indicate that the finding of intercellular C3 deposits in the absence of IgG in normal skin is not a sign of pemphigus but, rather, a sign either of an unusual type of drug reaction or, possibly, of some connective tissue disease. However, the finding of intercellular C3 plus IgG (with or without other immunoglobulins) is a sign of pemphigus. The mechanism of C3 deposition without immunoglobulins is not clear.

Adult↗
PubMedDate not supplied

Laser nephelometric assay of complements C3 & C4 in unselected Nigerian population.

The renewed interest in the routine clinical use of complement assays raises the need to obtain reference values in a denominator population as Nigerians. The present study used laser nephelometry to quantitate complement C3 and C4 proteins and obtained the means as 87.9mg/dl and 46.9mg/dl respectively. When compared with those of Central Europeans there was no statistical difference between the C3 levels of the two populations but C4 was significantly elevated among the Nigerians than the Europeans. This may suggest increased activation of the classical pathway.

Adult↗
PubMed1992

Effects of cell differentiation on the synthesis of the third and fourth component of complement (C3, C4) by the human monocytic cell line U937.

Association of complement synthesis with cell differentiation in U937 cells was investigated using granulocyte-macrophage colony-stimulating factor (GM-CSF), vitamin D3 and interferon-gamma (IFN-gamma) as differentiation-inducing agents. GM-CSF or vitamin D3 enhanced the synthesis of the third component of complement (C3) by U937 cells, but had no stimulatory effect on the synthesis of the fourth component of complement (C4). IFN-gamma increased both C3 and C4 synthesis by U937 cells. Combination of two of these three agents resulted in synergistic enhancement and all three agents caused maximal enhancement of C3 synthesis. Vitamin D3 enhanced IFN-gamma-induced C4 synthesis by U937 cells. These results were confirmed by ELISA and SDS-PAGE after biosynthetic labelling. GM-CSF, vitamin D3 or IFN-gamma increased the expression of complement receptor type 3 (CR3), one of the markers of monocyte/macrophage differentiation. Two of these agents caused a further increase and all three agents maximal increase in CR3 expression. Since C3 was synthesized in parallel with the degree of CR3 expression, the synthesis of C3, but not C4, by U937 cells is thought to be closely related to cell differentiation. It was reconfirmed that the synthesis of C3 and C4 by U937 cells was independently regulated.

Cell Differentiation↗
PubMed1975

Interactions of the third component of complement (C3) with cross-linked dextran. IV. Adherence of lymphocytes to C3 coated dextran gel particles.

In previous studies we could show that the third component of complement (C3) is bound from normal serum to cross-linked dextran (Sephadex) after activation via an alternate pathway. Data presented in this paper demonstrate that a subpopulation of human lymphocytes adheries to C3 coated Sephadex particles. The adhering subpopulation of lymphocytes is identical with or overlaps extensively with lymphocytes bearing easily detectable membrane Ig. This phenomenon can be used for the fractionation of lymphocyte subpopulations. After a single passage of tonsillar lymphocytes through C3 coated Sephadex bead columns, no membrane Ig positive lymphocytes were detectable in the effluent. 97-100% of effluent cells formed rosettes with untreated sheep red blood cells, thus resembling pure T cells. Apart from that, the use of C3 coated dextran gel particles allows also the recovery of adherent cells after dextranase digestion of the dextran gel particles. An investigation of retained cells showed enrichment of B cells, but also T cells were demonstrable. The retention of these T cells is probably due to nonspecific interactions.

Cell Separation↗
PubMed1977

Biosynthesis of the third component of complement (C3) in vitro by monocytes from both normal and homozygous C3-deficient humans.

Human monocytes synthesized the third component of complement (C3) up to 5 wk in vitro. Evidence for net C3 synthesis was based on (a) incorporation of 14C-labeled amino acids into C3 protein, (b) indentity of the allotype of C3 produced in vitro with that of the doner's serum C3, even in the presence of carrier C3 protein of a different allotype; (c) correspondence of electrophoretic mobility, size, and subunit structure of C3 protein produced in vitro with serum C3; (d) inhibition of C3 production with cycloheximide. Monocytes from two unrelated C3-deficient patients were studied under conditions that supported C3 synthesis by normal monocytes. Serum from each of the patients contained less than 1% of the normal C3 concentration, buth their monocytes produced C3 at approximately equal to 25% of the normal rate when studied after 2 wk in vitro. The C3 produced in vitro by monocytes from one of the patients had the molecular weight of normal serum C3 and dissociated appropriately under reducing conditions. Monocytes from C3-deficient patients could not be distinguished from normals on the basis of morphology, rosetting with C3-coated erythrocytes, or rates of C2, and total protein synthesis.

Blood Proteins↗
PubMed1977

Immunoelectronmicroscopical demonstration of in vivo bound complement C3 in psoriatic lesions.

The presence of in vivo bound complement (C3) within the stratum corneum of 4 psoriatic cases is demonstrated ultrastructurally by the use of the peroxidase-antiperoxidase multistep technique. The positive reaction product was located in the intercellular space and on the surface of the parakeratotic cells within the horny layer. The membranes of the horny cells were not altered and peroxidase granules could also not be detected within their cytoplasm. The explanation of this finding as well as its pathogenetic significance is discussed.

Animals↗
PubMed1992

Serum immunoglobulin and complement C3 levels in workers exposed to lead.

Serum immunoglobulin and complement C3 levels were measured in workers exposed to lead at a secondary lead refinery and a solder factory. In the first survey, significant correlations were found between blood lead and IgA with a correlation coefficient of 0.296, and between blood lead and IgE with a correlation coefficient of 0.314. No other significant correlations were found among the indicators of lead exposure and humoral immunity. In the second survey, no significant correlations were found between blood lead and IgG and IgA. A significantly higher number of subjects with IgE of more than 400 IU/ml was found in the group with blood lead of more than 60 micrograms/100 g.

Adolescent↗
PubMed1990

Molecular basis of complement C3 deficiency in guinea pigs.

In experiments to ascertain the biochemical basis of a genetically determined deficiency of the third component of complement (C3) in guinea pigs, we found that C3-deficient liver and peritoneal macrophages contain C3 messenger RNA of normal size (approximately 5 kb) and amounts, that this mRNA programs synthesis of pro-C3 in oocytes primed with liver RNA and in primary macrophage cultures. In each instance, heterodimeric native C3 protein was secreted with normal kinetics but the C3 protein product of the deficient cells failed to undergo autolytic cleavage and was unusually susceptible to proteolysis. These data and a selective failure of C3 in plasma of deficient animals to incorporate [14C]methylamine suggested either a mutation in primary structure of the C3 protein or a selective defect in co- or postsynthetic processing affecting the thiolester bridge, a structure important for C3 function. A mutation in the primary structure of C3 was ruled out by comparison of direct sequence analysis of C3 cDNA generated from two C3 deficient and two C3 sufficient guinea pig liver libraries. Three base pair differences, none resulting in derived amino acid sequence differences were identified. Finally, restriction fragment length polymorphisms were identified in the C3 gene that are independent of the deficiency phenotype. This marker of the C3 gene permits testing of these hypotheses using molecular biological and classical genetic methods.

Amino Acid Sequence↗
PubMed1990

Synthesis of the third component of complement (C3) by lectin-activated and HTLV-infected human T-cells.

The third component of complement (C3) plays key roles in complement activation of both the classical and alternative pathways. The liver is the major site of C3 synthesis; monocytes, B-lymphocytes and leukemic cell lines of the myeloid lineage also synthesize C3. Here we report that the C3 gene is inactive in fresh T-cells, but active in T-cells treated with the lectin phytohemagglutinin (PHA). Northern blot hybridization studies show that PHA-activated T-cells and all the T-cell lines tested express the 5.3 kb RNA transcript reported for C3 in HepG2, a hepatoma cell line, and monocytes. We used radioimmune precipitation followed by polyacrylamide gel electrophoresis to show that PHA-stimulated T-cells and T-cell lines, which are not infected with the human T-lymphotropic virus (HTLV), synthesize and release C3 proteins with molecular masses of 185, 115 and 80 kD; HTLV-infected T-cell lines release C3 proteins of 170, 115 and 70 kD. In contrast, monocytes produced C3 proteins of 115 and 70 kD similar to the serum form of this protein. The role of T-lymphocyte C3 and the implications of HTLV-infection are discussed.

Blotting, Northern↗
PubMed1985

Inhibition of cleavage of the third component of human complement (C3) by its small cleavage fragment, C3a: inhibition occurs with the classical-pathway, but not the alternative-pathway, C3 convertase.

Activation of the third component of complement (C), C3, is central to the functioning of the C system in inflammation. Cleavage of C3 by the C3 convertases of both the classical and alternative pathways results in the formation of two split products, C3b and C3a. C3a inhibited cleavage of C3 by the classical-pathway C3 convertase. The inhibition varied in a concn-dependent relationship, with a concn of approximately 40 micrograms/ml yielding 50% inhibition. Removal of the carboxy terminal arginine from the C3a did not alter the inhibition. C3a did not inhibit cleavage of C3 by the alternative C pathway C3 convertase, or cleavage of C5 by C5 convertase. The C3-cleaving capacity of EAC142oxy that had been previously incubated with C3a could be recovered completely by washing the cells, indicating that the C3a binding to the EAC42oxy cell must have been reversed without having had an effect on the amount of C2 bound. Ribonuclease, a molecule of similar size and charge to C3a, did not affect C3 cleavage and C3a inhibition was not reduced by providing a surface for non-specific adsorption of the C3a, suggesting that the effect of C3a on C3 cleavage was not mediated by non-specific interaction with cell surfaces. C3a inhibited the C3-cleaving capacity of the fluid-phase enzyme, C42oxy, to the same degree as it inhibited the cell-bound enzyme, EAC42oxy, indicating that the C3a must interact with the C42 complex directly. Inhibition of C3 cleavage by C3a is the first demonstration of product inhibition of a complement enzyme. It may provide another control of C3 activation.

Arginine↗
PubMed1990

[A comparative study of serum complement (C3 and C4) in inflammatory joint diseases].

The third and the fourth fraction of the complement (C3 and C4), haptoglobin, fibrinogen, alpha 1-glycoprotein, alpha 2-macroglobulin and transferrin were examined in 692 patients with inflammatory joint disease--rheumatism, rheumatoid arthritis, ankylosing spondylarthritis, psoriatic arthritis, Reiter's syndrome, sacroiliitis [correction of sacroileitis], reactive arthritis, gout, osteoarthrosis and nosologically undefined arthritis in active or nonactive phase and in 60 healthy controls. The complement fractions studied show an increase of various degree and importance in almost all groups of patients in both phases studied. The relations between the complement fractions and the other acute phase indices show significant correlations between them and the other acute phase indices. C3 and to a certain degree C4 could be added to the acute phase reacting indices. Their place in the downgrade scale is as follows: fibrinogen, haptoglobin, alpha 1-glycoprotein, C3, C4, alpha 2-macroglobulin, transferrin.

Acute-Phase Proteins↗
PubMed1989

Development of an enzyme-linked immunosorbent assay to detect IgG, IgM, and complement (C3) on canine erythrocytes.

An ELISA was used to detect IgG, IgM, and complement (C3) on the surface of canine erythrocytes. Erythrocytes were placed in wells of a microtitration plate and incubated with affinity purified, alkaline phosphatase-conjugated anti-canine IgG, IgM, or C3. Results of the ELISA were compared with the direct antiglobulin test (DAT) by preparing standard reference curves from canine blood type A erythrocytes that had been incubated with serial dilutions (1:2 to 1:8, 192) of canine anti-A serum. The ELISA detected increased erythrocyte-bound immunoglobulin and complement at two- to fourfold dilutions greater than those required for positive results with the DAT. The ELISA required small sample and reagent volumes and detected lower concentrations of immune components than did the DAT.

Animals↗