How to define the function of antibody?

Antibody: (immunoglobulin is not only an antibody) is a large Y-shaped protein secreted by plasma cells (effector B cells), which is used by the immune system to recognize and neutralize foreign substances such as bacteria and viruses. It only exists in the blood and other body fluids of vertebrates, and on the surface of the cell membrane of its B cells. Antibodies can recognize the unique characteristics of specific foreign objects, which are called antigens.

The main function of antibody is to combine with antigen (including foreign and self), so as to effectively remove foreign bodies such as microorganisms and parasites invading the body. Antibodies are protein produced in response to antigens, which can specifically bind to antigens. Each antibody binds to a specific antigenic determinant. This combination can inactivate the antigen, or it may be ineffective, but sometimes it will cause pathological damage to the body, such as the production of some autoantibodies such as antinuclear antibody, anti-double stranded DNA antibody and anti-thyroglobulin antibody, which will cause harm to the human body.