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Results for “Complement Pathway, Classical”

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PubMed1991

[Systemic lupus erythematosus associated with homozygous C2 deficiency. Apropos of a case report and literature review].

Inherited deficiencies of classical pathway complement components are rare and associated with autoimmune diseases and with increased susceptibility to bacterial infections. We report the clinical evolution and studies of the complement system in a 17-year-old female patient of Swiss origin presenting with systemic lupus erythematosus (malar rash, photosensitivity, leukopenia and antinuclear antibodies), in whom the hemolytically active second complement component (C2) was less than 10% of the normal value and antigenic C2 was not detectable. Linkage studies showed that the patient is HLA-A25, B18 positive and has the slow factor B allotype BfS. Further immunological assessment revealed low IgG4 concentrations in the patient, who had the G2M(23) allotype. The asymptomatic first degree family members had half-normal C2 levels compatible with a heterozygous state of C2 deficiency. Therapy with hydroxychloroquine for 17 months and topical sunscreen preparations produced marked clinical improvement. During the 4 years of follow-up, the patient has been well and shown only an abnormal titer of antinuclear antibodies. No infections were observed. To the best of our knowledge, 99 cases of homozygous C2 deficiency have been described so far and are discussed here.

Adolescent↗
PubMed1978

Heterogeneity of the clinical syndrome in patients with systemic lupus erythematosus and genetic deficiency of the second complement component.

Two patients with systemic lupus erythematosus associated with homozygous deficiency of the second complement component (SLE-C2D) illustrate the different clinical disease patterns found in patients with this illness. Despite the differences in extent and severity of clinical manifestations and serological findings, the renal disease was similar and kidney function was well preserved in both patients. Renal microscopic changes were focal and segmental, deposits of immuno-globulins and complement components were present by immunofluorescent staining, and dense deposits were seen by electron microscopy. Tubulo-reticular inclusion bodies were found in glomerular endothelial cells and lymphocytes of both patients, but not in the lymphocytes of a clinically healthy C2D sibling. The findings in these two patients stress the importance of careful evaluation to determine the presence of systemic disease in patients with SLE-C2D and suggest that an intact classic complement pathway is important in the development of severe lupus, nephritis, but is not needed in the pathogenesis of lupus skin lesions.

Adult↗
PubMed1990

[Current overview of diagnostic possibilities of complement analysis].

The complement system is composed of at least 21 serum proteins and 8 cell surface receptors sensitive to complement components or their fragments. Qualitative and quantitative analysis of complement components in clinical samples has become standard procedure in many laboratories thanks to the availability of easy-to-perform test kits. However, interpretation of results is still a task that requires great skill and the situation are rare, in which analysis of the complement system goes beyond diagnosis into therapeutic consequences. The present paper is an update of previous similar reviews now available in the international literature; in addition, the author attempts at bringing the often complicated world of complement and clinical practice together and thus contributes to answering the question: what should the clinician know about complement?

Antigen-Antibody Complex↗
PubMed1990

[Allergic reactions in treatment with L-asparaginase. Significance of specific IgE antibodies].

The formation of specific IgE antibodies to L-Asp was studied in 27 children with ALL. Increased titers of specific IgE antibodies were significantly more frequent (p less than 0.001) prior to L-Asp infusions followed by allergic reactions than in those without reactions. After passive sensitization of basophile granulocytes of a healthy volunteer using patient's serum with the highest titers of specific IgE antibodies to L-Asp a significant release of histamine was observed after exposure of cells to L-Asp. In 1 of 8 patients with allergic reactions titers of specific IgE antibodies were elevated, while there was not detectable activation of the complement system. In conclusion, elevated titers of specific IgE antibodies to L-Asp are frequently detectable prior to L-Asp infusions which are associated with allergic reactions. In addition to activation of the classical complement pathway specific IgE antibodies and mediator release from mast cells may contribute to clinical symptoms. In a small number of patients this mechanism alone may be responsible for the allergic reaction.

Adolescent↗
PubMed1975

Complement activation by interaction of polyanions and polycations. I. Heparin-protamine induced consumption of complement.

Interactions of heparin and protamine in fresh human serum, in amounts far below those required for complement depletion by either agent alone, were found to induce virtually complete depletion of total hemolytic complement activity. This depletion was dependent on time, temperature, pH, divalent cations, and serum concentration. The predominant complement component hemolytic activity depleted was C1; under appropriate reaction conditions C4 and C2 were depleted as well. Equivalent amounts of heparin along induced lesser but substantial depletion of C3-9, whereas equivalent amounts of protamine had no effect upon complement component activities. We conclude that interaction of heparin with protamine, like interaction of antibody with antigen, markedly enhances its ability to interact with the first component of complement and activate the classical complement pathway. It is suggested that complement activation by interactions between certain polyanions and polycations, like interactions between antigens and antibodies, may have a role in the initiation of inflammatory reactions.

Adult↗
PubMed1986

Assays for complement activation.

Complement is a major biologic mediation system that functions in host defense against microorganisms and other pathogens and also aids in the elimination of damaged and abnormal cells. This is accomplished by its ability to mediate the destruction of pathogens and altered cells directly through cytolytic and cytotoxic properties, as well as indirectly by its ability to augment the actions of various effector cells, which in turn destroy or inactivate these substances. Its second major action in vivo is the production of an acute inflammatory response that, by altering blood-vessel permeability, contracting smooth muscles, and promoting an influx of leukocytes, aids in the localization of the injurious process responsible for complement activation and retards its spread and dissemination throughout the body. The actions of the activated complement system upon pathogens and altered cells, as well as its phlogistic properties, are the direct consequence of the actions of complement protein-protein complexes, enzymes, peptides, and cleavage products on the activator, on biologic membranes, and on various effector and other tissue cells. Complement activation is a frequent phenomenon in infectious diseases, autoimmune diseases, and many other conditions having an inflammatory component. Because of the importance of this system in contributing to the resolution of the disease process, monitoring of the status of the system in patients is frequently indicated. Monitoring of the complement status is also appropriate in numerous other diseases, such as those with an inflammatory component, in which complement activation occurs secondarily but in which it is frequently responsible for confining the injurious process and aiding in its resolution. A number of techniques are available to assess the status of the complement system in samples obtained from patients. Among these are a group of newer tests that specifically detect complement activation. They quantitate activation-dependent complement cleavage products, antigenic changes, or protein-protein complexes. These tests are quantitative, highly sensitive, and extremely specific; furthermore, most can be employed with samples obtained from patients. Because all of the biologic actions of the complement system require complement activation, such newer activation-specific assays permit the precise evaluation of the status of this system in human diseases. Further extension of their use to additional patients and other disease complexes will undoubtedly increase the understanding of the biologic importance of the complement system in human disease processes.

Complement Activation↗
PubMed1989

Complement research.

Explore the source record for details and available documents.

Allergy and Immunology↗
PubMed1989

Distinct restriction of complement- and cell-mediated lysis.

Complement- and cell-mediated killing utilize related effector proteins (C8/C9 and perforin, respectively), suggesting that proteins which protect cells against complement- and cell-mediated attack may also be similar. In homologous complement-mediated killing two protective proteins, which are anchored to the cell membrane by phosphatidylinositol glycan (PIG) tails, are known. To study whether similar PIG-tailed proteins protect against lymphocyte-mediated killing, nucleated cell lines with a mutation in the biosynthesis of the PIG anchor were used. It was found that PIG-tailed membrane proteins restrict homologous complement-mediated lysis but not three different types of cell-mediated killing or lysis by purified perforin. Furthermore, E from patients with an acquired defect in PIG tail biosynthesis did not differ from normal E in sensitivity to antibody-dependent cell-mediated cytotoxicity, in spite of their increased sensitivity to human C8 and C9.

Antibody-Dependent Cell Cytotoxicity↗
PubMed1985

[Elimination of immune complexes: role of complement].

For many years it has been considered that complement does not modify the immune elimination of antigen-antibody complexes. However, recent studies suggest that complement contributes to the normal processing of immune complexes: (1) complement activation modifies the structure of the immune complex lattice and produces soluble complexes, (2) erythrocytes bind complement reacted complexes and deliver them to the fixed macrophage system. The clinical association between inherited complement deficiency and immune complex mediated diseases also suggests a role for complement in the physiological elimination of complexes.

Antigen-Antibody Complex↗