Question

The complement pathway is a critical mechanism for eliminating microbes, and is comprised of more than 30 proteins that are constitutively produced. Many of these proteins are synthesized as inactive pro-enzymes, and become active proteases when they are cleaved by an upstream member of the complement cascade. Importantly, the initiation of the complement cascade does not rely on the presence of antimicrobial antibodies, as:___________. 1. any antibody can activate the complement cascade, regardless of whether it has bound the pathogen 2. complement activation will induce antibody production 3. antibody-independent pathways of complement activation rely on complement components that directly bind to microbial surfaces 4. the pathway can still induce inflammation even in the absence of initiating signals to activate the complement cascade

Answer 1

3. Antibody-independent pathways of complement activation rely on complement components that directly bind to microbial surfaces.

Step-by-step explanation:

There are three pathways of complement activation:

• The classical pathway.
• The alternative pathway.
• The lectin pathway.

The classical pathway is triggered by binding of C1 either to the pathogen surface or to antibody bound to the pathogen.

The alternative pathway is triggered by the spontaneous hydrolysis of soluble C3 to C3(H₂O) and initiates eventual deposition of C3 convertase on microbial surfaces.

The lectin pathway is triggered by the binding of mannose-binding lectin or ficolins to carbohydrate residues in microbial cell walls and capsules.