Immunity Flashcards
(43 cards)
What is an antigen?
A molecule that triggers an immune response when detected by the body.
What are pathogens?
Microorganisms that cause diseases.
What are antibodies?
Proteins produced by B-cells that bind to complementary antigens.
Draw the general shape of an antibody.
Why can antibodies only bind to a specific antigen?
The variable region of the antibody has a specific tertiary structure, which is only complementary to one specific antigen.
Why is phagocytosis a part of the non-specific immune response?
It reacts with all pathogens in the same way.
Describe what happens in phagocytosis.
- The pathogens release toxins that attract the phagocyte towards it.
- The phagocyte engulfs the pathogen. This forms a vesicle called a phagosome.
- The phagosome fuses with a lysosome.
- The lysosome releases its lysosymes into the phagosome.
- These kill the pathogen by hydrolysis of their cell walls.
What are the two processes that are part of the specific immune response?
- Cellular response.
- Humoral response.
What is the cellular response?
The response of T-cells to foreign antigens.
What are T-cells?
Lymphocytes that are produced in the thymus gland.
Describe the cellular response.
- The phagocytes engulf the pathogen and display their antigen on its cell surface membrane.
- The T-cells have receptors on their cell membrane, that are complementary to that antigen.
- The antigen binds to the receptors and the T-cells replicate rapidly by mitosis.
- It produces cytotoxic cells and helper T-cells.
What is the role of the cytotoxic cells produced in the cellular response?
They kill abnormal body cells like tumour cells.
What is the role of the helper T-cells produced in the cellular response?
- They activate the phagocytosis of pathogens.
- They release chemicals that activate B-cells.
What is the humoral response?
The response of B-cells to foreign antigens. This involves the production of antibodies.
Where are B-cells produced?
The bone marrow.
Describe the humoral response.
- The B-cells have antibodies on their cell membrane that are complementary to a specific antigen.
- They also have receptors on their cell membrane that are complementary to the chemicals released by the T-cells.
- When the antibodies bind to the antigens and the chemicals bind to the receptors on the B-cells, they are activated.
- They divide and differentiate rapidly to form memory cells and plasma cells.
What is the role of the plasma cells?
They release antibodies which bind to antigens and cause them to stick together. This makes it easier for the pathogens to be engulfed and killed by phagocytes.
What is the role of the memory cells?
They stay in the blood for a long time. When they come across the pathogen again they divide and differentiate rapidly into plasma cells. The plasma cells then release antibodies.
Why is the secondary response faster than the primary response to infection?
The primary response involves the production of helper T-cells, the activation of B-cells and the B-cells binding to an antigen before plasma cells can be produced. The secondary response only needs the antigen to bind to the memory cells they then divide rapidly to form plasma cells that release antibodies.
What is passive immunity?
Antibodies are introduced into the body from an outside source.
Give an example of natural and artificial passive immunity.
Natural: antibodies received by a baby from its mother’s breast milk.
Artificial: monoclonal antibodies
What is active immunity?
Your immune system makes antibodies.
Give an example of natural and artificial active immunity.
Natural: exposure to diseases
Artificial: vaccines
What are vaccines?
Dead or inactive pathogens are injected into a patient to trigger an immune response