Capsules and M protein are thought to interfere with which...

Capsules and M protein are thought to interfere with which of the following?
a) Opsonization by complement proteins
b) Opsonization by antibodies
c) Recognition by T cells
d) Recognition by B cells
e) Phagosome-lysosome fusion

Key Concepts

Opsonization

Opsonization is the process by which pathogens are tagged for destruction by immune cells. This tagging is typically done by molecules such as antibodies and complement proteins, which bind to the surface of pathogens, enhancing their recognition and uptake by phagocytes.

Complement System

The complement system consists of a series of plasma proteins that work together to clear pathogens from an organism. One of its key roles is to opsonize bacteria, marking them for phagocytosis, as well as directly lysing cells through the formation of membrane attack complexes.

Bacterial Capsules

Bacterial capsules are external polysaccharide layers that envelop some bacteria, serving as critical virulence factors. They inhibit phagocytosis by masking surface antigens and interfering with the binding of opsonizing molecules, such as antibodies and complement proteins, thereby helping the bacteria evade the host’s immune system.

M Protein

M protein is a surface protein that acts as a virulence factor primarily in certain bacteria, contributing to immune evasion. It interferes with the complement cascade by binding factors that inhibit complement deposition on the bacterial surface, reducing opsonization and subsequent phagocytosis.

Immune Evasion

Immune evasion refers to the strategies employed by pathogens to avoid detection and destruction by the host’s immune system. Mechanisms such as the formation of capsules and the expression of specific surface proteins, like M protein, are used by bacteria to disrupt normal immune processes like opsonization and phagocytosis.

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