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Relationship between the component and regulatory proteins of the classical pathway C3 convertase. 1986

T R Welch, and J Forristal, and L Beischel

A relationship was found between the sums of the component proteins of the classical pathway C3 convertase (C2 and C4) and their regulators (C4bp and 1) in 184 normal controls. The relationship was maintained in most patients with low levels of individual components resulting from congenital deficiency and urinary losses, as well as in most cord sera. On the other hand, classical pathway activation in membranoproliferative glomerulonephritis type I, systemic lupus erythematosus, hereditary angioneurotic edema, and bacteremia resulted in loss of this relationship. Patients with alternative pathway-mediated complement activation (membranoproliferative glomerulonephritis type II) had a normal relationship between the classical component and regulatory proteins. In situations in which classical pathway activation is suspected, simultaneous examination of C4, C2, C4bp, and I may be helpful.

UI MeSH Term Description Entries
D008180 Lupus Erythematosus, Systemic A chronic, relapsing, inflammatory, and often febrile multisystemic disorder of connective tissue, characterized principally by involvement of the skin, joints, kidneys, and serosal membranes. It is of unknown etiology, but is thought to represent a failure of the regulatory mechanisms of the autoimmune system. The disease is marked by a wide range of system dysfunctions, an elevated erythrocyte sedimentation rate, and the formation of LE cells in the blood or bone marrow. Libman-Sacks Disease,Lupus Erythematosus Disseminatus,Systemic Lupus Erythematosus,Disease, Libman-Sacks,Libman Sacks Disease
D009393 Nephritis Inflammation of any part of the KIDNEY. Nephritides
D009404 Nephrotic Syndrome A condition characterized by severe PROTEINURIA, greater than 3.5 g/day in an average adult. The substantial loss of protein in the urine results in complications such as HYPOPROTEINEMIA; generalized EDEMA; HYPERTENSION; and HYPERLIPIDEMIAS. Diseases associated with nephrotic syndrome generally cause chronic kidney dysfunction. Childhood Idiopathic Nephrotic Syndrome,Frequently Relapsing Nephrotic Syndrome,Multi-Drug Resistant Nephrotic Syndrome,Pediatric Idiopathic Nephrotic Syndrome,Steroid-Dependent Nephrotic Syndrome,Steroid-Resistant Nephrotic Syndrome,Steroid-Sensitive Nephrotic Syndrome,Multi Drug Resistant Nephrotic Syndrome,Nephrotic Syndrome, Steroid-Dependent,Nephrotic Syndrome, Steroid-Resistant,Nephrotic Syndrome, Steroid-Sensitive,Nephrotic Syndromes,Steroid Dependent Nephrotic Syndrome,Steroid Resistant Nephrotic Syndrome,Steroid Sensitive Nephrotic Syndrome,Steroid-Dependent Nephrotic Syndromes,Steroid-Resistant Nephrotic Syndromes,Steroid-Sensitive Nephrotic Syndromes,Syndrome, Nephrotic,Syndrome, Steroid-Sensitive Nephrotic
D002352 Carrier Proteins Proteins that bind or transport specific substances in the blood, within the cell, or across cell membranes. Binding Proteins,Carrier Protein,Transport Protein,Transport Proteins,Binding Protein,Protein, Carrier,Proteins, Carrier
D003166 Complement Activating Enzymes Enzymes that activate one or more COMPLEMENT PROTEINS in the complement system leading to the formation of the COMPLEMENT MEMBRANE ATTACK COMPLEX, an important response in host defense. They are enzymes in the various COMPLEMENT ACTIVATION pathways. Activating Enzymes, Complement,Enzymes, Complement Activating
D003167 Complement Activation The sequential activation of serum COMPLEMENT PROTEINS to create the COMPLEMENT MEMBRANE ATTACK COMPLEX. Factors initiating complement activation include ANTIGEN-ANTIBODY COMPLEXES, microbial ANTIGENS, or cell surface POLYSACCHARIDES. Activation, Complement,Activations, Complement,Complement Activations
D003171 Complement Pathway, Classical Complement activation initiated by the binding of COMPLEMENT C1 to ANTIGEN-ANTIBODY COMPLEXES at the COMPLEMENT C1Q subunit. This leads to the sequential activation of COMPLEMENT C1R and COMPLEMENT C1S subunits. Activated C1s cleaves COMPLEMENT C4 and COMPLEMENT C2 forming the membrane-bound classical C3 CONVERTASE (C4B2A) and the subsequent C5 CONVERTASE (C4B2A3B) leading to cleavage of COMPLEMENT C5 and the assembly of COMPLEMENT MEMBRANE ATTACK COMPLEX. Classical Complement Pathway,Classical Complement Activation Pathway,Complement Activation Pathway, Classical
D003175 Complement C2 A component of the CLASSICAL COMPLEMENT PATHWAY. C2 is cleaved by activated COMPLEMENT C1S into COMPLEMENT C2B and COMPLEMENT C2A. C2a, the COOH-terminal fragment containing a SERINE PROTEASE, combines with COMPLEMENT C4B to form C4b2a (CLASSICAL PATHWAY C3 CONVERTASE) and subsequent C4b2a3b (CLASSICAL PATHWAY C5 CONVERTASE). C2 Complement,Complement 2,Complement Component 2,C2, Complement,Complement, C2,Component 2, Complement
D003179 Complement C3b The larger fragment generated from the cleavage of COMPLEMENT C3 by C3 CONVERTASE. It is a constituent of the ALTERNATIVE PATHWAY C3 CONVERTASE (C3bBb), and COMPLEMENT C5 CONVERTASES in both the classical (C4b2a3b) and the alternative (C3bBb3b) pathway. C3b participates in IMMUNE ADHERENCE REACTION and enhances PHAGOCYTOSIS. It can be inactivated (iC3b) or cleaved by various proteases to yield fragments such as COMPLEMENT C3C; COMPLEMENT C3D; C3e; C3f; and C3g. C3b Complement,C3bi,Complement 3b,Complement Component 3b,Inactivated C3b,iC3b,C3b, Complement,C3b, Inactivated,Complement, C3b,Component 3b, Complement
D003181 Complement C4 A glycoprotein that is important in the activation of CLASSICAL COMPLEMENT PATHWAY. C4 is cleaved by the activated COMPLEMENT C1S into COMPLEMENT C4A and COMPLEMENT C4B. C4 Complement,C4 Complement Component,Complement 4,Complement C4, Precursor,Complement Component 4,Pro-C4,Pro-complement 4,C4, Complement,Complement Component, C4,Complement, C4,Component 4, Complement,Component, C4 Complement,Pro C4,Pro complement 4

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