Ans:The Mode of Action of Vaccines
Pathogens contain special proteins called "antigens". When pathogens enter 1. the body (blood) of host, these proteins stimulate the immune response in host -l i.e. synthesis of "antibodies". Antibodies bind to pathogens and destroy them. In addition, "memory cells" are produced, which remain in blood and provide ''• protection against future infections with the same pathogen.