Describe how a vaccine leads to production of antibody against the disease (4 marks)

This question is asking for an outline of how antibody is produced in an immune response, and for the 4 marks, we need to identify 4 or more steps using key words in this process. This question could also be asked in the context of a bacteria or virus infection instead of a vaccine. As this question is asking for how an antibody is made, further information about the structure or function of the antibody is not needed. 1) A vaccine contains antigens of the pathogen being vaccinated against. (Antigens are the molecules or parts of a pathogen that immune system cells can recognise). 2) Antigen is displayed on antigen-presenting cells. (These are the cells that detect and take up the antigen to show it to the lymphocytes). 3) Helper T cells recognise the antigen and stimulate B cells. (Helper T cells "help" the B cell become activated by recognising the antigen). 4) B cells undergo clonal expansion and differentiate into plasma cells. Plasma cells produce antibodies. (The B cells divide by mitosis and undergo changes to form the plasma cells which can produce the antibodies).