C4

Background

Human C4 is a glycosylated protein originating from the human leukocyte antigen system. C4 is homologous to complement C3 and C5, sharing ~30% homology with them. Mature C4 is a trimer protein complex composed of three polypeptide chains: α chain, β chain, and γ chain, which provides a surface for interaction between the antigen-antibody complex and other complement components. In complement cascade, once the complement classical pathway or the lectin pathway were activated, the related activated proteases C1s or MASP-2 immediately cleave complement component 4 (C4) into two fragments C4a and C4b, simultaneously, cleave complement component 2 (C2) into two fragments C2a and C2b.

C4, a key member of the complement system, is cleaved into C4a and C4b upon catalyzed by C1s or MASP-2. C4b fragment is highly reactive and participates in the formation of the C3 convertases (C4bC2b) and C5 convertases (C4bC2bC3b) in the classical pathway and lectin pathway. C4a is an anaphylatoxin that mediates local inflammatory reactions. There are two common isoforms found in humans, C4A and C4B, whereas, only C4B in animals. The expression C4 directly determines the activation of the complement system. It has been reported that C4 abnormity is associated with a series of human diseases, such as complement dysfunction, immunodeficiency, systemic lupus erythematosus, and schizophrenia.

Fig.1 Fragmentation of complement C4 activation.¹

C4 Functional Service

Creative Biolabs provides a comprehensive range of Complement C4-related products, encompassing anti-C4 Antibodies, Complement C4 ELISA Assay Kits, recombinant and native C4 Proteins, which are essential for functional assays, allowing precise detection and quantification of C4 activity. Our high-quality C4 proteins and antibodies ensure accurate functional analysis in complement activation studies, immune response research, and disease-related investigations.

Fig.2 Anti-inflammatory functions of complement C4 activation fragments.¹

C4 Functional or Activity Test focuses on assessing the functional integrity of Complement C4 in various biological contexts. These tests aim to evaluate the ability of C4 to activate and participate in the classical and lectin complement pathways, crucial for immune defense and inflammation modulation. Methods for C4 activity testing include ELISA-based assays, hemolytic assays, and functional assays using recombinant C4 proteins. Our complement C4 products enable researchers to perform reliable functional assays that measure C4 activation, binding, and interactions with other complement proteins. These tests are particularly useful in understanding complement dysregulation in autoimmune diseases, inflammatory disorders, and C4 deficiencies. Furthermore, our advanced C4 assays assist in pharmaceutical research to develop therapeutic strategies targeting the complement system.

Creative Biolabs provides C4-functional services, including customized assay development, data analysis, and technical support for C4 activity testing. Our experts help optimize assays to meet specific research needs, offering fast turnaround and reliable results.

Click the following targets to view our C4 product lists.