When complement proteins are covalently deposited onto the surface of a bacterium, this can sometimes lead to direct lysis of the bacterium. However, more commonly, the deposition of complement proteins onto the bacterial surface does not directly harm the bacterium. Instead, these complement proteins aid in bacterial elimination by:
A) Recruiting antibodies to the bacterial surface, leading the antibody-dependent neutralization
B) Providing a mechanism for phagocytes to use their Fc receptors to recognize and ingest the bacterium
C) Cross-linking carbohydrate structures on the bacterial surface, thereby preventing the bacterium from replicating
D) Stimulating B lymphocytes to produce more antibodies against the bacterium
E) Providing a mechanism for phagocytes bearing complement receptors to recognize and ingest the bacterium

Question

Quizplus · Accepted Answer

When complement proteins are deposited onto the bacterial surface, they can act as opsonins, meaning they can help to "tag" the bacterium for phagocytosis by cells like macrophages and neutrophils. These cells have complement receptors on their surface, allowing them to bind to and engulf the bacterium. Therefore, choice E is the best answer.

When Complement Proteins Are Covalently Deposited onto the Surface of a Bacterium