25. People may be immunised against diseases using vaccines. (a) (i) Which part of the vaccine stimulates the body's defence system? (ii) A person has been vaccinated against measles. The person comes in contact with the measles pathogen. The person does not catch measles. Explain why.

Question

25. People may be immunised against diseases using vaccines. (a) (i) Which part of the vaccine stimulates the body's defence system? (ii) A person has been vaccinated against measles. The person comes in contact with the measles pathogen. The person does not catch measles. Explain why.

Answer 1

(a) (i) The part of the vaccine that stimulates the body's defence system is an attenuated or dead form of the pathogen, also known as an antigen, which confused the immune system into thinking it's being invaded, promoting it to fight back.(ii) The vaccinated person does not catch measles because their immune system has previously encountered the weakened or dead measles pathogen through the vaccine. This previously incited an immune response establishing an immunological memory in the form of T and B lymphocytes; when the same pathogen tries to invade again, the immune system swiftly recognises and fights it, paired with the mass production of lymphocytes that know how to combat measles, thus preventing sickness.

Answer 2

## Step1: Discuss how vaccines work in general and how it activates our immune system. ### The part of a vaccine that stimulates the body's defence system is an attenuated (weakened) or dead form of the pathogen, or some small part of the pathogen, like the protein on the coating of a virus. ## Step2: Describe the principle of memory cells and the role Julia play in our immune response.### When a body gets vaccinated against measles, the vaccine introduces the attenuated or the dead form of measles pathogen into the immune system. This causes an immune response and the body reacts by producing a specific type of lymphocytes (white blood cells) known as T and B cells. These T and B cells have a unique ability to remember the foreign antigen/pathogen. So, when a person comes in contact with the measles pathogen after vaccination, the defense system recognizes the antigens on the pathogen and responds swiftly. This involves the rapid multiplication of lymphocytes that are able to recognize for the pathogen such that it suppresses the infection before it has time to cause the disease.

Question

25. People may be immunised against diseases using vaccines. (a) (i) Which part of the vaccine stimulates the body's defence system? __ (ii) A person has been vaccinated against measles. The person comes in contact with the measles pathogen. The person does not catch measles. Explain why. __

Answer

Answer

Explanation

25. People may be immunised against diseases using vaccines. (a) (i) Which part of the vaccine stimulates the body's defence system? (ii) A person has been vaccinated against measles. The person comes in contact with the measles pathogen. The person does not catch measles. Explain why.