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[Proteins of the complement system in normergy and anergy on mycobacterial antigens].

The influence of the immunization of mice with different doses of BCG (Mycobacterium bovis) vaccine strain on the state of their complement system was studied. The presence of essential differences in the functional activity of proteins in the development of the state of anergy and in normal immune response was established. The animals with the opposite sensitivity to M.bovis were found to have not only initially different levels of the activity of complement proteins, but also different variants of the reaction of their complement system in response to the injection of BCG vaccine. The state of anergy was characterized by an increase in the total activity of the classical activation path and simultaneously by the tendency to a decrease in functionally active molecules of some components of the classical path. The states of anergy and normal response differed in the links and character of relationships between components. Thus the functional state of the complement system was closely linked with the type of immunobiological processes in the cell element of immunity.

Animals↗
PubMed1994

Aberrant expression of membrane cofactor protein and decay-accelerating factor in the endothelium of patients with systemic sclerosis. A possible mechanism of vascular damage.

BACKGROUND: One of the main features of systemic sclerosis (SSc) is vascular damage, the mechanism of which is not understood. The aim of this study was to investigate if complement (C) regulatory molecules, membrane cofactor protein (MCP), decay-accelerating factor (DAF), and CD59, which normally protect endothelial cells from damage by autologous C, are absent or down-regulated in vascular endothelium of patients with SSc. A deficiency or persistent down-regulation of the above molecules is likely to render vascular endothelium of these patients susceptible to damage by physiologically or pathologically activated C. From this point of view, expression of MCP, DAF, and CD59 was tested on endothelium of skin of normal subjects and patients with diffuse and limited forms of SSc. EXPERIMENTAL DESIGN: Punch biopsies of normal skin (N = 11) and lesional and non-lesional skin of patients with diffuse (N = 5) and limited (N = 5) forms of SSc were obtained and serial sections prepared. Immunoperoxidase staining of these sections was carried out using four monoclonal antibodies (MoAbs) directed to different epitopes of DAF, four to different epitopes of MCP, one to CD59 and one to von Willebrand factor. von Willebrand factor served as a marker of endothelial cells. Besides normal skin, lesional skin of systemic lupus erythematosus and several inflammatory and proliferative diseases, described below, served as controls. RESULTS: The endothelium of normal skin strongly expressed all the three proteins. However, the endothelium of lesional and nonlesional skin of all the 10 patients with diffuse or limited forms of the disease tested, expressed either decreased or undetectable amounts of MCP and DAF. CD59 expression was normal in some patients and lower than normal in others. Aberrant expression of MCP, DAF, or CD59 was not found in other control inflammatory, connective tissue and proliferative diseases studied. CONCLUSIONS: In view of the common function of MCP and DAF to protect self cells from autologous C, their decrease or virtual absence from the endothelium of patients with SSc strongly suggests that this deficiency may contribute to vascular damage, resulting in intima proliferation and, finally, fibrosis.

Antibodies, Monoclonal↗
PubMed2003

Diversity in intrinsic strengths of the human complement system: serum C4 protein concentrations correlate with C4 gene size and polygenic variations, hemolytic activities, and body mass index.

Among the genes and proteins of the human immune system, complement component C4 is extraordinary in its frequent germline variation in the size and number of genes. Definitive genotypic and phenotypic analyses were performed on a central European population to determine the C4 polygenic and gene size variations and their relationships with serum C4A and C4B protein concentrations and hemolytic activities. In a study population of 128 healthy subjects, the number of C4 genes present in a diploid genome varied between two to five, and 77.4% of the C4 genes belonged to the long form that contains the endogenous retrovirus HERV-K(C4). Intriguingly, higher C4 serum protein levels and higher C4 hemolytic activities were often detected in subjects with short C4 genes than those with long genes only, suggesting a negative epistatic effect of HERV-K(C4) on the expression of C4 proteins. Also, the body mass index appeared to affect the C4 serum levels, particularly in the individuals with medium or high C4 gene dosages, a phenomenon that was dissimilar in several aspects from the established correlation between body mass index and serum C3. As expected, there were strong, positive correlations between total C4 gene dosage and serum C4 protein concentrations, and between serum C4 protein concentrations and C4 hemolytic activities. There were also good correlations between the number of long genes with serum levels of C4A, and the number of short genes with serum levels of C4B. Thus, the polygenic and gene size variations of C4A and C4B contribute to the quantitative traits of C4 with a wide range of serum protein levels and hemolytic activities, and consequently the power of the innate defense system.

Adult↗
PubMed2004

Complement and autoimmune glomerular diseases.

The renal glomerulus is the specialized structure in the kidney responsible for generating over 150 liters of plasma ultrafiltrate per day in humans. Certain characteristics of this structure favor involvement in autoimmune diseases. Formation of immune complexes in the glomerulus, either deposited from the circulation or generated in situ, can activate the complement system. Active products of this system include the anaphylatoxins C3a and C5a, C3b, which covalently associates with immune complexes, and the C5b-9 membrane attack complex. If complement is activated in a site accessible to blood constituents, such as in the subendothelial and mesangial regions, generated C3a, C5a and C3b can interact with their respective receptors on inflammatory cells to lead to an exudative lesion. In addition, intrinsic glomerular cells bearing relevant receptors may also be activated and can proliferate to contribute to the inflammation. In a privileged site such as the subepithelial region, complement activation products are not accessible to blood cells, and as such, the resultant pathology is noninflammatory. In this setting, effects of C5b-9 predominate, which include activation and injury of cells through still incompletely characterized pathways. Various means to alter the complement pathway are now available, including antibody inhibitors and recombinant proteins based upon naturally occurring complement regulators. The use of these agents, as well as mice in which individual components of the complement system have been deleted, has given a great deal of insight into how the complement system is involved in glomerular disease. The ability to manipulate the complement pathway is now a reality in a clinical setting, yet conclusive human studies are difficult to achieve.

Animals↗
PubMed1998

Transgenic mice overexpressing the complement inhibitor crry as a soluble protein are protected from antibody-induced glomerular injury.

Complement receptor 1-related gene/protein y (Crry) is a potent murine membrane complement regulator that inhibits classical and alternative pathway C3 convertases. In nephrotoxic serum (NTS) nephritis, injected antibodies (Abs) bind to glomeruli, leading to complement activation and subsequent glomerular injury and albuminuria. To study the phenotypic effects of continuous complement pathway blockade, transgenic mice were created that express recombinant soluble (rs) Crry directed by the broadly active and heavy metal-inducible metallothionein-I promoter. One transgenic line expressing high levels of rsCrry was propagated. Serum rsCrry levels were 18.7 +/- 2.7 microg/ml (n = 5) at basal level and increased to 118.1 +/- 20.6 microg/ml 4 d after addition of zinc to the drinking water. By reverse transcription polymerase chain reaction (RT-PCR), transgene messenger (m)RNA was present in liver, kidney, brain, lung, and spleen, but not in heart. By in situ RT-PCR analysis of kidneys, transgene mRNA was widely expressed both in renal glomeruli and tubules. Urinary excretion of rsCrry was 113.4 +/- 22.4 microg/ml with a fractional excretion relative to creatinine of 13.2 +/- 2.7%, consistent with local renal production of rsCrry and secretion into urine. The founder and all transgene positive adult animals have remained healthy with no mortality or apparent phenotypic abnormalities, including infection or immune complex disease. To determine whether rsCrry blocked complement-mediated injury, NTS nephritis was induced by injection of NTS immunoglobulin (Ig)G, followed by an 18-h urine collection to quantitate the excretion of albumin as a measure of glomerular injury. In transgene-negative littermates (n = 15), transgene-positive animals (n = 10), and transgene-positive animals fed zinc (n = 10), albuminuria was 4,393 +/- 948, 1,783 +/- 454, and 1,057 +/- 277 microg/mg creatinine, respectively (P < 0.01 by ANOVA). Glomerular C3 was evident by immunofluorescence staining in 12/15 transgene-negative animals, but in none of the transgene-positive animals fed zinc. Thus, we have produced the first transgenic animals that overexpress a soluble C3 convertase inhibitor. rsCrry expression markedly ameliorates an Ab-induced disease model in vivo. These results support the hypothesis that continuous complement inhibition at the C3 convertase step is feasible and effective in complement-mediated injury states.

Animals↗
PubMed1994

Therapeutic regulation of the complement system in acute injury states.

The study of the intrinsic regulation of complement has uncovered a broad array of proteins with differing specificities and physicochemical properties. This will allow application of these proteins, native or modified, to the problem of controlling inflammation. The availability of sCR1, as the first such agent, has permitted further definition of those adverse clinical situations which are complement-dependent. The use of sCR1 as a drug might be anticipated in situations of thermal injury, ARDS, septic shock, and ischemia/reperfusion injury, such as myocardial infarction after thrombolytic therapy. sCR1 may also serve as the tool with which to unravel and possibly treat xenograft rejection. It can be anticipated that other such specific inhibitors will become available.

Animals↗