Explain the principle behind Immunisation. Name any two diseases that can be prevented by Immunisation.
Answers
Immunization is the process whereby a person is made immune or resistant to an infectious disease, typically by the administration of a vaccine. Vaccines stimulate the body's own immune system to protect the person against subsequent infection or disease.
The immune system consists of trillions of specialised blood cells, known as white blood cells, and their products, such as antibodies. These cells are located throughout the body, not only in the bloodstream, but also in lymph glands, the spleen, the skin, lungs and intestine.
The skin and the lining of the lungs and intestine are the first line of defence against infection. These tissues and the white blood cells located at these sites form the innate immune system (see Figure 1.1) 15,16. The white blood cells of the innate immune system (or guardian white blood cells) detect the presence of infection using sensors on their surfaces that recognise parts of pathogens or the toxins released by them. These fragments from pathogens or toxins are collectively known as antigens (see Question 2).
When guardian white blood cells detect the presence of pathogens, a second set of white blood cells (called lymphocytes 17) is activated (see Figure 1.1). Lymphocytes are categorised into two types: B-cells and T-cells. 18-20
T-cells respond to infections by releasing chemicals called cytokines, which trigger protective inflammation. Furthermore, T-cells can help combat pathogens by killing cells that harbour a pathogen hidden inside them. 21 B-cells, sometimes with help from T-cells, make antibodies, which are complex proteins that attach in a ‘lock-and-key’ fashion either to pathogens or to the toxins released by them. When antibodies attach to a pathogen, they flag it for destruction, and when they attach to a toxin, they neutralise its ability to cause damage. 14,15
In most cases, the outcome of these immune responses is termination of the infection followed by repair of any associated damage to the body’s tissues. However, some infections outstrip the immune system’s capacity to respond, leading to disease and sometimes death. By giving a vaccine before exposure to the infection, such serious outcomes can be avoided through generation of protective immunity in advance.
Diseases that can be prevented by Immunisation are measles, mumps, rubella, MMR, yellow fever, varicella, rotavirus, and influenza (LAIV).
Answer:
The body builds up immunity through this vaccine for the disease rabies. This process has proved beneficial in preventing several infectious diseases and has decreased the mortality rate to a great extent. There are vaccines against tetanus, smallpox, measles etc.
Explanation: