Question

The primary role of complement control proteins that operate in the early stages of complement activation is to _____.

a. regulate the expression of complement proteins
b. ensure that the components of the membrane-attack
complex assemble in the correct sequence
c. facilitate the secretion of complement proteins to
extracellular locations
d. stabilize complement proteins, thus extending their
half-lives in serum
e. ensure that C3b is deposited on appropriate surfaces.

Answer 1

Complement control proteins mainly ensure the appropriate deposition of C3b on pathogen surfaces as part of the immune response to facilitate the lysis of pathogens.

Step-by-step explanation:

The primary role of complement control proteins that operate in the early stages of complement activation is to ensure that C3b is deposited on appropriate surfaces.

Complement proteins are part of the immune system and have various functions, one of which is marking pathogens for phagocytosis, a process termed opsonization. They are produced by the liver and macrophages, are abundant in the blood serum, and participate in the innate immune response, primarily through the alternate pathway, and in the adaptive immune response through the classical pathway.

Binding of these proteins to the surface of microorganisms happens in a precise and regulated sequence, initiated via cleavage and/or structural changes by antibodies bound to pathogens, swiftly leading to the pathogen being coated in complement proteins. Regulatory proteins control this binding to prevent complement activation on host cells, ensuring C3b, a crucial element of the complement system, is deposited only on foreign entities such as bacteria, where it can then join with other components to form pores and lyse the pathogenic cells.