Immunity past paper questions Flashcards
Explain why individuals of blood group O are regarded as universal donors, while those of blood group AB are universal recipients
There are no antigens present in blood group O, so can be safely donated
-Blood group AB has no antibodies, so any antigen can be given.
With reference to T-Lymphocytes, explain why non-self skin from a donor is rejected
T-Lymphocytes have specific receptors on their cell surface membrane, which attach to the complementary viral antigens on the cell surface membrane on the antigen presenting cell. These T- Lymphocytes become activated/ sensitised and divide by Mitosis (clone). These clones develop into Killer T-cells.
Outline the function in defending the human body against bacterial infection
Skin- produces fatty acids (sebum) to kill bacteria
-Tear fluid- contains Lysozomes which digest cell walls of bacteria
-Gastric Juice- occurs in stomach (hydrochloric) which kills bacteria in food and water consumed
Explain how children being injected with a weakened strain of TB bacteria, can result in long term immunity
-A weakened strain is non- pathogenic bacteria, recognised as foreign/non self. Antigen/antibody mediated immunity is produced, where memory cells are produced. Memory cells persist, giving long-term immunity. On second exposure, memory cells are programmed to respond quickly.
Describe the precise location of the blood antigens
Plasma membrane of red blood cells
State the antigen present when the blood plasma contains antibody B
Antigen A
Describe the process of Agglutination
If incompatible blood is given, then the body produce antibodies that bind with the antigens on the surface of the introduced red blood cells, resulting in them clumping together. This is known as Agglutination, which can block small blood vessels, and cause kidney damage.
Antibodies are proteins produced and secreted by plasma cells in response to the presence of foreign antigens. Describe how plasma cells are produced in response to a foreign antigen
Plasma cells are derived from B-Lymphocytes. A specific cell is sensitised/ antigen binds to a specific receptor. The cell divides by mitosis, producing a clone. Some of which develop into plasma cells ( memory cells also produced).
Describe two adaptations of plasma cells for the production of large quantities of antibodies.
- Many mitochondria are present to provide energy for the production of antibodies.
- Nucleus- production of RNA/ ribosomes
- RER- translation/ production of proteins
- Golgi- modification/ packaging (into vesicles) of protein produced.
Describe how tears act as a barrier to entry
Tears contain the lysozome enzyme, to break down microbes, and wash away debris/ pathogens from the front of the eye
Using the understanding of protein structure, explain why protein is suitable for the role of antibodies.
Proteins have a GLOBULAR structure, each protein has a SPECIFIC SHAPE, which is COMPLEMENTARY to the shape of an antigen
Suggest how previous infection with similar viruses may have made older people immune to swine flu, so preventing them becoming ill
The similar antigens would be detected, and memory cells are produced in response to the earlier virus. If infected with swine flu/ virus stimulates plasma cell production/ killer T cell production/ secondary production. Plasma cells secrete antibodies which are complementary to the antigens, with complementary receptors, through antigen-antibody reaction (agglutination)/ T killer cells destroy infected cells. This is a rapid response, preventing illness.
Outline what happens during the primary immune response
Helper T-cells bring antigen/ pathogen to the B Lymphocyte. A specific B Lymphocyte must come into contact with the antigen in the blood (body fluids). The matching B Lymphocyte divides (Mitosis- clone), to produce plasma cells. This delay characterises the antibody response. Plasma cells begin antibody productions, and antibodies destroy pathogens.
How is long term immunity against a pathogen carrying this antigen?
Memory cells are produced, which respond rapidly to the presence of the pathogen. The pathogens are destroyed before they can multiply enough to cause damage.
How does the immune response to transplanted tissue from another individual (non related) differ from the response to the injection of an antigen?
-T-Lymphocytes are involved instead of B- Lymphocytes.
-Antibodies are not released/ held onto the cell surface membrane.
-Greater differentiation of cells (Killer T-cells, instead of plasma cells).
-T-Killer cells result in lysis whereas antibody-antigen reactions vary, eg agglutination
Describe one way in which the problems of tissue rejection may be overcome
The use of X-rays, which irradiates bone marrow and lymph tissue, to inhibit the production of lymphocytes and slow down rejection.
How to know when a vaccination is given
-A delay period during which B-cells are sensitised (recognised the antigens), and plasma cells are produced (cloning0 and antibodies are synthesised.
What do you understand by the term “rhesus positive”
An individual whose red blood cells contain antigen D/ rhesus antigen/ agglutination
What would need to enter the mother’s blood from the baby’s blood to produce the above immune response?
Blood cells containing the rhesus antigen
Describe the sequence of events which will occur in the mother’s blood (Rh-) after exposure to the baby’s blood (Rh+).
-The rhesus antigen is recognised as ‘non self’/’foreign’
-foetal rhesus antigen stimulates mothers B Lymphocytes
-B Lymphocytes divide rapidly to produce clone cells.
-Plasma cells produce antibodies
-Response characterised by delay/ time to produce plasma cells
-Memory cells retain ability to activate antibody response to second meeting.
Explain how this more intense immune response is produced following the second rhesus positive pregnancy
Memory cells are retained after stimulation by first childs rhesus antigen. This allows for more rapid production of antibodies. Allows geater antibody production leads to greater destruction of red blood cells.
Suggest how the “anti-D” injection stops the mother’s body from recognising the baby’s rhesus positive red blood cells and explain how it would therefore protect the baby
-Binds to the receptor sites on the B-Lymphocytes in the mother
-binds to the rhesus antigens, in the baby’s red blood cells.
-The B- Lymphocytes of the mother can’t respond to produce antibodies.
Explain how a vaccine containing weakened (attenuated) virus particles, results in long term immunity
The virus antigens are recognised by B- Lymphocytes, which clone to produce memory cells (and plasma cells), on subsequent exposure, memory cells produce antibodies which neutralise the infecting virus particles, known as the Secondary Response.
Explain why more than one dose of a vaccine may be necessary
-number of memory cells decrease over time
-booster vaccine activates memory cells so more are produced
-provide longer term immunity
