C3b/iC3b, Human, mAb 5G9

The Vital Role of C3b/iC3b in Complement System Activation

C3 plays a pivotal role in activating the complement system, a key component of our immune response. This activation is crucial for both the classical and alternative complement pathways. A deficiency in C3 can increase susceptibility to bacterial infections, underlining the importance of understanding the C3b/iC3b dynamic.

C3 Convertases: The Pathway to C3b/iC3b Formation

One form of C3 convertase, C4b2a, is vital in the classical and lectin pathways. It catalyzes the cleavage of C3 into C3a and C3b. While C3a functions as an anaphylotoxin and cytokine precursor like ASP, C3b acts as an opsonizing agent. The transformation of C3b into C3c and C3d, facilitated by Factor I, plays a crucial role in enhancing B cell responses. In the alternative pathway, C3b is also generated by C3bBb, another form of C3 convertase, leading to the creation of the C3b/iC3b forms.

Mechanics of C3b/iC3b in Immune Regulation

Once formed, C3b can bind to surfaces via a reactive thioester, a crucial step in the complement activation process. The alternative pathway’s C3 convertase, C3bBb, undergoes deactivation in several steps. Initially, the Bb component is removed by proteins with decay-accelerating factor activity. Subsequently, C3b is methodically broken down to iC3b, then to C3c and C3dg, and finally to C3d. This process, involving Factor I and CR1 as a cofactor, is pivotal in the regulation of the complement system.

Clinical Relevance of C3b/iC3b Levels in Diagnosis

Monitoring levels of C3, and by extension C3b/iC3b, in the blood can provide valuable diagnostic insights. For example, low levels of C3 are linked with certain kidney diseases such as post-infectious glomerulonephritis and shunt nephritis. Understanding the behavior and levels of C3b/iC3b is thus critical in both the diagnosis and potential treatment of various medical conditions.

Not sure which C3 antibody to use?

With numerous options available, it is essential to select the right C3 antibody to ensure the success of your research. We designed a guide to assist you in making an informed decision:

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