Which of the following are the pathways of the complement system?

The pathways of the complement system, which is an essential component of the immune response, include the classical, lectin, and alternative pathways. Each of these pathways plays a crucial role in activating the complement system, which leads to opsonization of pathogens, recruitment of inflammatory cells, and lysis of microorganisms.

The classical pathway is typically initiated by the binding of antibodies to antigens on the surface of pathogens, leading to a cascade of complement activation. The lectin pathway is triggered by the binding of lectins (carbohydrate-binding proteins) to specific sugars on microbial surfaces, which similarly activates the complement cascade. The alternative pathway functions independently of antibodies and can be initiated directly on microbial surfaces, providing a rapid response to infection.

The other options do not accurately describe the specific pathways associated with the complement system. Understanding these pathways is vital in the context of immune responses and pathology, particularly with regard to how the body defends against infections and what can go wrong in immune-related diseases.