What happens to an antigen-antibody complex?

An antigen-antibody complex can undergo several different processes depending on the specific context and the immune response:

Neutralization: In many cases, the formation of an antigen-antibody complex leads to the neutralization of the antigen. This means that the antigen is prevented from exerting its harmful effects. For example, in the case of bacterial or viral infections, the antibodies produced by the immune system can bind to the antigens on the surface of the pathogens, preventing them from infecting cells.

Opsonization: Opsonization is the process by which antigens are coated with antibodies to enhance their recognition and phagocytosis by phagocytic cells such as macrophages and neutrophils. When antibodies bind to antigens, they act as a signal for phagocytic cells, facilitating the engulfment and destruction of the antigen-antibody complexes.

Complement activation: Binding of antibodies to antigens can activate the complement system, which is a group of proteins that work together to enhance the immune response. Complement activation can lead to the formation of membrane attack complexes (MAC) that create pores in the membranes of target cells, causing cell lysis and destruction.

Antibody-dependent cell-mediated cytotoxicity (ADCC): Some antibodies can directly trigger the killing of target cells through ADCC. This process involves the binding of antibodies to antigens on the target cell surface, followed by the recruitment of effector cells such as natural killer (NK) cells or macrophages. These effector cells then recognize the antibodies and release cytotoxic molecules that lead to the destruction of the target cell.

Immune complex formation: In some cases, antigen-antibody complexes can form soluble complexes that circulate in the bloodstream. These immune complexes can be deposited in various tissues, leading to immune complex-mediated diseases or inflammation if not efficiently cleared by the immune system.

It's important to note that the exact fate of an antigen-antibody complex depends on factors such as the type of antigen, the class and specificity of antibodies involved, and the overall immune response of the individual.