Splitting the complement protein (C3) into C3a and C3b as a result of contact with the Fc region of antibodies coating a bacterium illustrates the onset of which of the following ?Choose from the following:(A) classical pathway of complement activation(B) alternate pathway of complement activation In the diagram, we see a simplified representation of how antibodies interact with microbes. The labeled parts include:1. **Microbe with Antigens**: The microbe is depicted as a green oval shape with small red markers on its surface, representing antigens. These antigens are specific molecules that trigger an immune response.2. **Antibodies**: These are illustrated by Y-shaped structures in purple. Antibodies bind to antigens on the microbe's surface. 3. **C1**: Represented as a purple circle beneath the antibodies, labeled "C1." This is likely referencing the C1 complex in the complement system, a part of the immune response that enhances the ability to clear microbes.Arrows indicate interactions, showing that antibodies recognize and attach to the antigens on the microbe, which can then lead to further immune actions such as the activation of the complement system (beginning with C1). This diagram is useful for understanding how the immune system identifies and responds to foreign invaders.

The complement system is a collection of more than 20 proteins that circulate in blood and tissue fluids.The majority of the proteins are usually inactive, but they become sequentially activated in an enzyme cascade in response to the identification of molecular components of microbes. When one protein is activated, the next protein in the cascade is cleaved and activated enzymatically. Major histocompatibility complex(MHC) III is also responsible for synthesizing the complement proteins . The complement system play important role in lysising the bacterial and viral infected cells, opsonization of the pathogen, promote inflammation, and provide immune clearance to the body. The classical pathway of complement activation involves the phenome, which occurs when the complement protein (C3) is split into C3a and C3b as a result of interaction with the Fc region of antibodies coating a bacterium. The Fc (Fragment, Crystallizable) region is made up of two heavy chains, each of which contributes two or three constant domains, depending on the antibody type.The Fc region ensures that each antibody develops a proper immune response for a given antigen by attaching to certain proteins. The complement components C1, C2, and C4 are involved in this process.Antibody-antigen complexes bind to C1, which has three subcomponents: C1q, C1r, and C1s.The route produces C4b2a, a C3 convertase that separates C3 into two fragments: C3b, which can covalently bond to the surface of microbial pathogens and opsonize them, and C3a, which activates mast cells and causes the production of vasoactive mediators like histamine. As a result, the above statement depicts the commencement of the classical pathway of complement activation. Hence, option (A) is correct.The alternative pathway is triggered by chemicals embedded in invading bacteria' surface membranes and does not require the presence of antibodies. This is spontaneously activated by the hydrolysis of C3 protein. C3 protein interacts with all surfaces of bacteria, fungal cell wall teichoic acid. This pathway involves a number of components, including B, D, H, and I, which interact with one another and with C3b to generate a C3 convertase, C3bBb, which can activate more C3, hence the name 'the amplification loop.'The loop is activated when bacteria and fungal cell walls are present, but it is blocked when chemicals on the surface of normal mammalian cells are present. Thus, there is no Fc region involved in the activation of this pathway as this is the non-antibody-dependent pathway. Hence, option (B) is incorrect.The classical pathway illustrates the involvement of the Fc region in the activation of the complement pathway as it is activated by the antigen-antibody complex. Thus, the classical pathway of complement activation is correct.