Antibodies protect the body from disease through various mechanisms, primarily by recognizing and neutralizing pathogens or marking them for destruction. Here are two key ways they achieve this:
1. Neutralization
Neutralization is a direct way antibodies prevent pathogens from causing harm. Antibodies bind to specific sites on the pathogen, such as those needed to infect cells.
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Blocking Attachment: By binding to the pathogen's surface proteins that are essential for attaching to and entering host cells, antibodies effectively prevent the pathogen from infecting new cells. This renders the pathogen harmless because it can no longer replicate or spread within the body.
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Example: Antibodies targeting the spike protein of SARS-CoV-2 neutralize the virus by preventing it from binding to the ACE2 receptor on human cells, thus blocking viral entry.
2. Opsonization
Opsonization involves antibodies coating pathogens, making them more easily recognized and engulfed by phagocytic immune cells (like macrophages and neutrophils).
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Enhanced Phagocytosis: Phagocytes have receptors that bind to the constant region (Fc region) of antibodies. When antibodies coat a pathogen, they act as a "flag" for phagocytes, signaling them to engulf and destroy the pathogen. This process dramatically increases the efficiency of phagocytosis.
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Example: Antibodies bound to bacteria can enhance their uptake and destruction by macrophages, preventing the bacteria from multiplying and causing infection.
In summary, antibodies protect the body by directly neutralizing pathogens, preventing them from infecting cells, and by opsonizing pathogens, making them more susceptible to phagocytosis.
