Question

3 pathways that the complement cascade can be activated, where they converge

A) Classical, alternative, and lectin pathways; Convergence at C3
B) Classical, lectin, and oxidative pathways; Convergence at C5
C) Alternative, oxidative, and lectin pathways; Convergence at C1
D) Classical, alternative, and oxidative pathways; Convergence at C4

Answer 1

The complement system is activated through three pathways: classical, alternative, and lectin, which converge at the activation of the C3 component. Classical pathway is initiated by C1 binding to an antibody, alternative pathway starts spontaneously by pathogen presence, and lectin pathway commences when mannose-binding lectin binds to a pathogen's surface.

Step-by-step explanation:

The complement system can be activated through three main pathways which eventually converge at a common point in the cascade. The three pathways are the classical, alternative, and lectin pathways. They converge at the activation of the C3 component. More specifically:

• The classical pathway is initiated by the binding of the complement protein C1 to an antibody that is attached to a foreign substance, typically a pathogen.
• The alternative pathway is activated spontaneously by pathogens themselves without the need for antibodies.
• The lectin pathway is triggered when mannose-binding lectin (MBL), a type of acute-phase protein, binds to carbohydrates on the surface of a pathogen.

All three pathways result in the activation of a sequence of events that lead to the cleavage of the C3 component, a pivotal step in the complement cascade, and to subsequent immune responses such as opsonization, cell lysis, and inflammation.