Vaccination is based on the principle of

Option 1, 2, 3, 4 - Natural active immunity: It is acquired by natural clinical or subclinical infections. Such natural immunity is longlasting. For example, individuals suffering from smallpox become immune to second attack of the disease. - Aificial active immunity: It is induced in individuals by vaccines. There is a wide range of vaccines available against many microbial pathogens. These may be live vaccines, killed vaccines, or vaccines containing bacterial products. therefore Immunologic Memory is created AGGLUTINATION- type of antigen antibody reaction Phagocytosis- process of engulfment of paicles, micro-organisms by cells Clonal Detection-By contact with self-antigens during development,self-tolerance is developed by clonal deletion