What is immunisation?

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Hint: Immunisation occurs after vaccination. It is the process of the production of antibodies against diseases.

Complete Answer:
Immunisation is the process by which the body produces antibodies against diseases, under the influence of vaccines. These are mainly used against bacterial and viral diseases in both humans and cattle.
The process of introduction of a vaccine into an individual to provide its immunity against disease is called vaccination.

- A vaccine is a suspension of dead or attenuated disease-causing microorganisms, which on injecting into a healthy individual provides temporary or permanent immunity (active or passive).
- Immunisation mainly boosts the memory of the organism's own immune system and helps in the generation of more memory-B and memory-T cells that help in faster pathogen recognition.
- Immunisation harnesses the body's innate immune system. The white blood cells or leukocytes and their antibodies in the body provide the immunity.
- The WBCs detect the presence of infections with the help of their antibodies binding to the surface antigens of the pathogens.
- The second set of WBCs called lymphocytes are produced that are further categorized into B-cells and T-cells.
- T-cells release chemicals called cytokines as a response to the infection. This triggers protective inflammation at the site of entry of infection.
- T-cells also kill pathogens harboring cells in a mission to combat the disease. B-cells with the help of T-cells produce antibodies that bind to the antigens on the pathogen surface or the toxins released by them.
- When the antibody and antigen complex is formed, that particular cell is flagged for destruction.

Note: Vaccination before the introduction of the infection into the host body helps in immunization. Serious outcomes can be avoided by providing protective immunity in advance.