A decrease in the production of C3 would result in
a. increased susceptibility to infection.
b. increased numbers of white blood cells.
c. increased phagocytosis.
d. activation of C5 through C9.
e. none of the above

Verified step by step guidance

1. Understand the role of C3 in the immune system. C3 is a crucial component of the complement system, which enhances the ability of antibodies and phagocytic cells to clear microbes and damaged cells.
2. Recognize that a decrease in C3 production would impair the complement system's ability to opsonize pathogens, leading to reduced phagocytosis.
3. Consider the impact on the immune response: with less C3, the formation of the membrane attack complex (MAC) through the activation of C5 to C9 would be hindered.
4. Evaluate the potential outcomes: reduced C3 levels would likely lead to increased susceptibility to infections due to impaired opsonization and MAC formation.
5. Analyze the options: increased susceptibility to infection (a) is a direct consequence of decreased C3, while the other options do not logically follow from reduced C3 production.

Key Concepts

Complement System

The complement system is a crucial part of the immune response, consisting of a series of proteins that enhance the ability of antibodies and phagocytic cells to clear pathogens. C3 is a central component of this system, playing a key role in opsonization, inflammation, and cell lysis. A decrease in C3 production can impair these functions, leading to increased vulnerability to infections.

Opsonization

Opsonization is the process by which pathogens are marked for destruction by immune cells. This is often facilitated by complement proteins, particularly C3b, which binds to the surface of pathogens, enhancing their recognition and uptake by phagocytes. A reduction in C3 would lead to decreased opsonization, resulting in a diminished immune response against infections.

Phagocytosis

Phagocytosis is the process by which certain immune cells, such as macrophages and neutrophils, engulf and digest pathogens and debris. This process is significantly enhanced by the presence of opsonins, including C3b. If C3 levels are low, the efficiency of phagocytosis is reduced, leading to an increased risk of infection and a slower immune response.