Antibodies and vaccination

Structures and Functions of Antibodies

Antibodies, also known as immunoglobulins, are proteins produced by B-cells (a type of white blood cell) in response to a foreign substance, or antigen.
Each antibody has two unique sites that can bind to specific antigens, allowing them to lock onto and neutralise specific pathogens.
Antibodies have a Y-shaped structure with variable regions at the tips of the arms that bind to the antigens. The variation in these regions allows for a match to any possible antigen.
The constant region at the stem of the Y is the same in all antibodies of the same class and can bind to receptors on immune cells.
Antibodies can help destroy pathogens by opsonisation (making them easier to engulf by phagocytes), neutralisation (binding to the surface of the pathogen to prevent it from entering host cells), and agglutination (clumping pathogens together to immobilise and easier disposal).

Vaccination is the process of introducing a harmless form of a pathogen (antigen) into the body to stimulate the immune system to produce a response.
The aim of a vaccine is to produce memory cells that allow for a quick and strong response (secondary immune response) if the real pathogen encounters the body in the future.
Vaccines can contain live, weakened pathogens, inactivated or killed pathogens, or isolated antigens from the pathogen.
By stimulating an immune response without causing the disease, vaccines provide active immunity against future infections.
Herd immunity occurs when a high percentage of the population is vaccinated, reducing the overall amount of pathogen able to spread within the community. This helps protect individuals who can’t be vaccinated due to health reasons.