Question

The complement system serves as an effector arm of both innate and acquired immunity. Comprised of over 30 circulating and membrane-fixed proteins, complement acts in a wide variety of host defenses, inflammatory, homeostatic, and immune reactions. The most important action of complement is to facilitate the uptake and destruction of pathogens by phagocytic cells. Patients with deficiencies of C1, C2, C3, and C4 have increased infections with encapsulated organisms (S. pneumoniae, S. pyogenes, H. influenzae) because of the critical role of the early components of complement in what process?

Opsonization
Neutralization
Phagocytosis
Pinocytosis
Endocytosis

Answer 1

The critical role of the early components of the complement system (C1, C2, C3, and C4) is in the process of opsonization, which facilitates pathogen destruction by phagocytic cells.

Step-by-step explanation:

The most important action of complement, during both innate and acquired immune responses, is to facilitate the uptake and destruction of pathogens by phagocytic cells through the process of opsonization.

In opsonization, complement proteins bind to the pathogen's cell membrane, effectively marking it for phagocytosis by immune cells such as macrophages and neutrophils.

Deficiencies in the early components of the complement system (C1, C2, C3, and C4) impair this critical process, leading to increased susceptibility to infections by encapsulated organisms, such as Streptococcus pneumoniae, Streptococcus pyogenes, and Haemophilus influenzae.