Immunology & Disease

Question 1

What are some natural barriers against infection in humans?

Answer 1

› Skin provides a tough physical barrier
› Skin flora (harmless bacteria) stop pathogens from colonising the skin
› Blood clotting seals wounds
› Stomach lining produces stomach acid
› Respiratory tract lined with cilia and goblet cells
› Tears, saliva, and stomach acid contain lysozyme

Question 2

What are the four main symptoms of inflammation and what are its functions?

Answer 2

› Symptoms are pain, redness, heat, and swelling

› To destroy cause of infection, limit the effects on the body it can have, and replacing or repairing damaged tissue

Question 3

What is an antigen?

Answer 3

› A foreign substance which provokes an immune response

› And induces the formation of antibodies

Question 4

What are the two systems of immunity in mammals?

Answer 4

› Cell-mediated immune response

› Humoral immune response

Question 5

What does cell-mediated immunity involve?

Answer 5

› T-lymphocytes from the thymus gland found circulating in the blood and lymph
› When encountering a virus, T-lymphocytes divide by mitosis, and then differentiates into four cells types

Question 6

What are the four cell types that T-lymphocytes differentiate into?

Answer 6

› T-killer cells, to recognise foreign antigens and cause their target cells to lyse
› T-helper cells, to secrete chemical messengers known as cytokines
› T-memory cells, remain dormant in blood, giving an immunological memory
› T-suppressor cells, slow down immune response on recovery

Question 7

What does humoral immunity involve?

Answer 7

› B-lymphocytes produced in the bone marrow are used
› Microbe engulfed by a phagocyte, activating the B-lymphocytes to divide by mitosis
› Majority are plasma cells which produce antibodies, some become memory B-cells, which remain in the blood until the antigen is met again

Question 8

What is the difference between the primary immune response and the secondary immune response?

Answer 8

› Primary immune response has a longer latent period and a low level of antibody is produced
› Secondary immune response has a very short latent period due to memory cells, and antibody levels stay high for a longer time

Question 9

What is the difference between active immunity and passive immunity?

Answer 9

› Active immunity is when the body makes its own antibodies (either by being exposed to an infection, or by having an antigen injected (a vaccine))
› Passive immunity is when an individual receives antibodies produced by another individual (either from the mother’s placenta to the foetus, or by injecting ready-made antibodies)

Question 10

What are the ways in which vaccines are made?

Answer 10

› Using dead pathogens that still posses the antigenic sites
› Using live, non-virulent strains (e.g. with Rubella)
› Modified toxins
› Isolated antigens separated from a pathogen