Question

The complement cascade involves a series of proteins that circulate in the blood. There are three pathways that lead to activation of the complement cascade--classical, alternative, and lectin. Your goal is to enhance the immediate response to bacterial infection. With this goal in mind, why might you choose to target the lectin or alternative pathways rather than the classical?

Choose the statement that best describes why the lectin or alternative pathway would stimulate a more immediate response than the classical pathway.

Answer 1

To enhance the immediate immune response to bacterial infection, the lectin or alternative pathways should be targeted as they do not require antibody production. The alternative pathway activates spontaneously, and the lectin pathway is triggered by binding of certain proteins to pathogen surfaces.

Step-by-step explanation:

To enhance the immediate response to bacterial infection, targeting the lectin or alternative pathways of the complement cascade would be more effective than the classical pathway. The alternative pathway can be triggered spontaneously without the need for antibodies, using the C3 convertase to break down C3, which directly binds to pathogens lacking host regulatory proteins, leading to lysis. In contrast, the classical pathway requires the presence of antibodies bound to the pathogens, making it dependent on the adaptive immune response, which takes longer to activate as it involves the body identifying the pathogen and producing specific antibodies.

In the case of the lectin pathway, it is activated by the binding of mannose-binding lectin to the pathogen surface. This does not require the production of antibodies, thus allowing faster activation compared to the classical pathway. Therefore, both the lectin and alternative pathways enable rapid activation of the complement system as part of the innate immune response, providing a swift defense against bacterial invasion.