Is C1q a complement protein?

Is C1q a complement protein?

The complement component 1q (or simply C1q) is a protein complex involved in the complement system, which is part of the innate immune system. C1q together with C1r and C1s form the C1 complex. Antibodies of the adaptive immune system can bind antigen, forming an antigen-antibody complex.

What is C1q?

C1q is a complex glycoprotein assembled from 18 polypeptide chains, with a C-terminal globular head region that mediates recognition of diverse molecular structures, and an N-terminal collagen-like tail that mediates immune effector mechanisms.

Where is C1q made?

C1q is the initiation molecule of the classical pathway of the complement system and is produced by macrophages and immature dendritic cells.

What does C1q function?

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.

What does C1q recognize?

C1q, the ligand-binding unit of the C1 complex of complement, is a pattern recognition molecule with the unique ability to sense an amazing variety of targets, including a number of altered structures from self, such as apoptotic cells.

What is anti C1q IgG?

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.

How many complement proteins are there?

The complement system consists of more than 30 proteins that are either present as soluble proteins in the blood or are present as membrane-associated proteins.

How many polypeptides are associated with the formation of C1q molecules?

The C1q complex is composed of 18 polypeptide chains.

What does high C1q mean?

The presence of C1q antibodies in SLE is associated with severe illness, often with renal involvement. The highest concentrations are associated with disease relapse, when the level of C1q simultaneously is low. High concentration of antibodies usually decreases rapidly in response to treatment.

What is anti C1q antibody?

What is a C1q blood test?

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.

Why are complement levels low in lupus?

Background. Lupus patients usually have low C3 and C4 levels during disease flares because of activation of the complement system by immune complexes (ICs) [1]. However, in remission periods, complement levels reach normal values.

What is C1q of the complement pathway?

Complement protein C1q, the recognition molecule of the classical pathway, performs a diverse range of complement and non-complement functions. It can bind various ligands derived from self, non-self, and altered self and modulate the functions of immune and non-immune cells including dendritic cells and microglia.

What is complement C1q quantitative?

What is C1q antibody?

Anti-C1q antibodies (Anti-C1q Ab) are seen in hypocomplementemic urticarial vasculitis syndrome (HUVS), infection-associated vasculitis such as hepatitis C virus-related vasculitis and in autoimmune diseases such as rheumatoid vasculitis, polyarteritis nodosa, giant cell arteritis, vascular Behcet’s disease, and …

What causes low C1q?

These decreased C1q levels can be caused by defective production (preeclampsia, minority of SLE patients, RA, emphysema), increased consumption (majority of SLE patients, some HUVS patients, acquired angioedema), and/or depletion by immune complexes or anti-C1q autoantibodies (HUVS).

What does positive C1q mean?

Interpretation. 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 molecular weight of C1q?

C1q Protein. Purified human complement component C1q. Circulating C1q protein is a hexamer of three unique protein subunits (A, B, and C) with molecular weights of 29, 26 and 22 kD respectively. The assembled hexamer contains a central core or stalk, 6 collagen-like domains and 6 globular protein heads.

Is C1q a lectin?

Complement component C1q is a calcium-dependent sugar-binding protein, a lectin, belonging to the collectin family of proteins, which contains both collagen-like and lectin domains hence the name collectin. It has six globular heads, linked together by a collagen-like tail, which surround the (C1r:C1s)2 complex.

Is the C1q pathway innate or adaptive?

The classical pathway plays a role in both innate and adaptive immunity.C1q family proteins are characterized by a distinctive ‘globular domain’ of about 140 amino acids (the gC1q domain) situated at the carboxyl terminus of a collagen ‘stalk’.

What is complement component C1q?

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. C1q can, however, also bind directly to the surface of certain pathogens and thus trigger complement activation in the absence of antibody.