What is the Primary mechanism of antibody action?

Neutralization: This is the primary mechanism of antibody action. Antibodies can bind to and neutralize pathogens such as bacteria or viruses, preventing them from infecting host cells. Neutralization can occur by blocking the pathogen's attachment to host cells, inhibiting its entry into host cells, or interfering with its function.

Opsonization: Antibodies can also act as opsonins, promoting the phagocytosis (ingestion) of pathogens by immune cells such as macrophages and neutrophils. Antibodies bind to antigens on the pathogen's surface, making them more recognizable and easier for phagocytes to engulf.

Complement activation: Antibodies can activate the complement system, a cascade of proteins that leads to the destruction of pathogens. When antibodies bind to antigens on the pathogen's surface, they can trigger the classical complement pathway. This pathway involves the sequential activation of several complement proteins, resulting in the formation of a membrane attack complex that punctures the pathogen's cell membrane and causes cell lysis.

Antibody-dependent cell-mediated cytotoxicity (ADCC): Antibodies can also mediate ADCC, a process in which immune cells such as natural killer (NK) cells or macrophages kill target cells coated with antibodies. When antibodies bind to antigens on the target cell's surface, they can recruit NK cells or macrophages and activate them to release cytotoxic molecules that destroy the target cell.

In addition to these main mechanisms, antibodies are also involved in other immune functions such as antibody-dependent phagocytosis (ADP) and antibody-mediated inflammation. Antibodies are essential components of the humoral immune response and play a vital role in protecting the host against infections.