What is the C1 complex composed of?
The C1 complex is composed of 1 molecule of C1q, 2 molecules of C1r and 2 molecules of C1s, or C1qr2s2.
Is C1q an antibody?
C1q antibodies have primary been studied in systemic lupus erythematosus (SLE) and Hypocomplementemic urticarial vasculitis syndrome (HUVS), a SLE-like disease. The presence of C1q antibodies in SLE is associated with severe illness, often with renal involvement.
What is the function of C1q?
A classical function of C1q is to bind immune complexes and initiate complement activation producing membrane lytic complexes, opsonins and anaphylatoxins. This classical pathway of complement activation is also elicited when C1q binds some other ligands.
Where is C1q located?
C1q is composed of 18 polypeptide chains: six A-chains, six B-chains, and six C-chains. Each chain contains a collagen-like region located near the N terminus and a C-terminal globular region. The A-, B-, and C-chains are arranged in the order A-C-B on chromosome 1.
What produces C1?
C1q is an abundant plasma protein. It can be produced broadly in tissues by macrophages and DCs, which also produce C1r/C1s. C1q is formed from three similar but distinct subunits, i.e., A, B, and C, and the order of assembly is illustrated.
What is C1 in complement system?
Complement Component C1 Background The classical pathway plays a role in both innate and adaptive immunity. Complement component C1q, the first component of this pathway, links the adaptive humoral immune response to the complement system by binding to antibodies complexed with antigens.
What is C1q antibody?
Anti-C1q antibody (Anti-C1q Ab) develops in disorders characterized by immune complex mediated injury, more commonly in skin and glomerular microvasculature. 1 Anti-C1q Ab are IgG antibodies bound to collagen like C1q.
What is a C1q antibody test?
This test is used to monitor proliferative lupus nephritis (LN) disease activity and help assess the likelihood of LN flares in individuals with systemic lupus erythematosus.
What happens if C1q is inhibited?
This peptide inhibits the recognition phase of the classical pathway, namely the binding of C1q, resulting in inhibition of subsequent activation of C4 and C3, formation of the membrane attack complex, and erythrocyte lysis.
What does low C1q mean?
C1q deficiency is a rare immunodeficiency, which is strongly associated with the development of systemic lupus erythematosus (SLE). A mutation in one of the C1q genes can either lead to complete deficiency or to low C1q levels with C1q polypeptide in the form of low-molecular weight (LMW) C1q.
What is a C1q level?
C1q identifies and binds to immunoglobulin complexed to antigen and activates the complement cascade. C1q levels serve as an indicator of the amount of C1 present. The C1q Blood Test measures levels of C1q to help diagnose an inherited or acquired C1 deficiency.
What is C1 in the complement system?
Complement component C1 circulates in the plasma as a huge, inactive protein complex containing one C1q subunit, two C1r subunits and two C1s subunits. The C1q subunit can bind to the Fc regions of two antigen-specific antibodies that have bound in close proximity to antigen fixed on the surface of a pathogen.