Indicators
A protein complex composed of 18 complement component 1q (C1q) subcomponent chains: six C1qA, six C1qB and six C1qC. The C1q complex is part of the complement component C1 complex (C1 complex) and undergoes confirmational rearrangement following binding of pentraxins or antigen-antibody complexes that include either immunoglobulin M (IgM) or several IgG molecules. These confirmational changes activate the C1r chains of the C1 complex, which, in turn, cleaves C1s chains of the C1 complex. Following C1s cleavage, the C1 complex can proteolytically activate C2 and C4 and promotes formation of C3-convertase, which cleaves C3 and activates the classical complement pathway.
Indicators
The most abundant immunoglobulin G (IgG) subclass in the circulation of healthy individuals. The IgG1 core hinge sequence contains 15 amino acids and two interchain disulfide bonds. This subtype has high affinity for binding both Fc receptors and complement component C1q. IgG1 is the predominant antibody subclass that responds to antigens derived from both soluble and membrane proteins. Reduced levels of circulating IgG1 can indicate the presence of a variety of primary and secondary antibody deficiencies, which can result in hypogammaglobulinemia.
Indicators
The second most abundant immunoglobulin G (IgG) subclass in the circulation of healthy individuals. The IgG2 core hinge sequence contains 12 amino acids and up to four interchain disulfide bonds. This subtype has low affinity for binding both Fc receptors and complement component C1q. The production of this IgG2 is stimulated by exposure to bacterial capsular polysaccharides and other antigenic glycans.
Indicators
Along with the immunoglobulin G4 subclass (IgG4), the IgG3 subtype makes up a minor part of circulating antibodies in healthy individuals. The core hinge sequence contains approximately four times the number of amino acids as the other subclasses; allotypes of IgG3 can have up to 62 hinge residues and up to four interchain disulfide bonds. The increased hinge size for IgG3 increases the separation between the Fc (constant fragment) tail and Fab (antigen binding fragment) arms of antibodies of this subclass. This enhances the relative flexibility of the molecule, which may modulate antigen-binding capacity and immune complex formation, and may increase the affinity for binding to both Fc receptors and complement component C1q.
Indicators
Along with the immunoglobulin G3 subclass (IgG3), the IgG4 subtype makes up a minor part of circulating antibodies in healthy individuals. The IgG4 core hinge sequence contains 12 amino acids and two interchain disulfide bonds.This subtype has moderate affinity for binding Fc receptors and does not bind complement component C1q. The production of IgG4 can be stimulated following repeated or long-term exposure to antigen. Elevated levels are found in various diseases and infections and can be indicative of an fibroinflammatory syndrome known as IgG4-related disease.
Product
Clinical Chemistry
Product
Clinical Chemistry
Technology
A measurement of the antibody or complement-coated erythrocytes in a blood specimen in vivo.
Diagnostic Methods
Technology
A laboratory procedure in which an RNA strand is first transcribed into a DNA complement and then subjected to PCR amplification. Transcribing an RNA strand into a DNA complement is termed reverse transcription and is done by the enzyme reverse transcriptase.
Diagnostic Methods
Indicators
Adiponectin (244 aa, ~26 kDa) is encoded by the human ADIPOQ gene. This protein is involved in the modulation of both glucose metabolism and lipid homeostasis.
Tests
An immunoassay that detects bladder cancer antigen, which is comprised of various members of the complement factor H-related protein (CFHrp) family, in urine.
For professionals
Tests
The determination of cellular CD21 expression in a biological specimen.
For professionals
