title: Relationship between the component and regulatory proteins of the classical pathway C3 convertase.
abstract: 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.
mesh_terms: D000799:Angioedema / Q000276:immunology; D002352:Carrier Proteins / Q000172:deficiency / Q000378:metabolism; D003166:Complement Activating Enzymes / Q000378:metabolism*; D003167:Complement Activation; D003175:Complement C2 / Q000172:deficiency / Q000378:metabolism; D050577:Complement C3-C5 Convertases / Q000378:metabolism*; D003179:Complement C3b / Q000378:metabolism; D003181:Complement C4 / Q000172:deficiency / Q000378:metabolism; D003171:Complement Pathway, Classical; D005312:Fetal Blood / Q000276:immunology; D005921:Glomerulonephritis / Q000276:immunology; D006801:Humans; D016167:Integrin alphaXbeta2; D008180:Lupus Erythematosus, Systemic / Q000276:immunology; D009393:Nephritis / Q000209:etiology; D009404:Nephrotic Syndrome / Q000276:immunology; D018805:Sepsis / Q000150:complications / Q000276:immunology
chemical_list: D002352:Carrier Proteins; D003175:Complement C2; D003181:Complement C4; D016167:Integrin alphaXbeta2; D003179:Complement C3b; D003166:Complement Activating Enzymes; D050577:Complement C3-C5 Convertases