Antibodies & vaccination

This lesson explains how the body defends itself with antibodies and how vaccines put that defence to work. We build the antibody molecule piece by piece — a Y-shaped protein of four polypeptide chains, two heavy and two light, held by disulfide bonds, with a variable region that carries two specific antigen-binding sites, a constant region and a flexible hinge — and relate that structure directly to its functions: agglutination, neutralisation, opsonisation and forming the antigen-antibody complex. We outline how monoclonal antibodies are made by the hybridoma method and how they are used in diagnosis (pregnancy tests, ELISA, disease markers) and in targeted treatment of disease. We then separate active from passive immunity and natural from artificial immunity in a four-way table, explain how vaccines contain antigens that stimulate an immune response and leave memory cells for long-term immunity, and finish with how national vaccination programmes create herd immunity and can even eradicate a disease such as smallpox.