C4c Human

Complement Component C4c is a fragment of the complement system, which is a crucial part of the immune system. The complement system consists of a series of small proteins that enhance (or “complement”) the ability of antibodies and phagocytic cells to clear pathogens from an organism. Complement Component C4c is derived from Complement Component 4 (C4), which plays a significant role in the classical and lectin pathways of the complement system .

Complement Component 4 (C4) is a glycoprotein composed of three polypeptide chains: alpha (α), beta (β), and gamma (γ). The C4 protein is cleaved into C4a and C4b by the enzyme C1s during the activation of the complement system. C4b then binds to the pathogen surface and forms a complex with C2a, creating the C3 convertase (C4b2a), which is essential for the activation of the complement cascade .

C4c is a degradation product of C4b. It is generated when C4b is cleaved by factor I in the presence of cofactors such as complement receptor 1 (CR1) or membrane cofactor protein (MCP). The cleavage of C4b results in the formation of C4c and C4d. C4c is released into the plasma, while C4d remains bound to the cell surface .

Complement Component C4c, as part of the complement system, plays a vital role in the immune response. The complement system helps to clear pathogens, promote inflammation, and enhance the ability of antibodies to neutralize pathogens. C4c, being a fragment of C4b, indirectly contributes to these processes by being a marker of complement activation .

The levels of Complement Component C4c in the blood can be used as a biomarker for various diseases. Elevated levels of C4c can indicate increased complement activation, which is often seen in autoimmune diseases such as systemic lupus erythematosus (SLE) and rheumatoid arthritis. Conversely, low levels of C4c may suggest a deficiency in the complement system, which can lead to increased susceptibility to infections .