• There are four types of white blood cell: phagocytes, granulocytes, T lymphocytes and B lymphocytes.
• Phagocytes trap antigens in phagosomes which then fuse with liposomes that release digestive enzymes called lipases.
• Granulocytes release histamines and prostaglandins to stimulate the primary response.
• Antigens are found on all cells within a body and are specific to that body.
• B-lymphocytes secrete immunoglobulins.
• Antibodies are composed of a constant region and variable regions.
• T-lymphocytes bind to the antigen of pathogens with their receptor proteins.
• Antigen-presenting cells are created when macrophages ingest foreign cells causing the antigens of the microbe to appear on the surface of the macrophages
• Clonal selection is the process in which B and T lymphocytes divide to produce an army of clones.
• Cellular immunity refers to T-lymphocytes destroying foreign cells directly.
• Humoral immunity refers to foreign cells being destroyed by soluble antibodies.
• Memory cells means that if the same antigen attacks the body againg the clones needed can be produced much faster: the secondary immune response.
• Some pathogens are capable of antigenic variability.
• Vaccination means that a body can produce the right antibodies without suffering from the disease first.
• Passive immunity involves the actual antibodies being injected into a patient as opposed to them making them themselves.
• Monoclonal antibodies are produced in vivo and can be used to track down specific proteins.
• There are a number of ethical issues surrounding vaccines and monoclonal antibodies.

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TEST IT!

Pathogens can cause disease when they enter a host body.
a) Name two ways in which they cause disease.
i. ____________________________________________________________
ii. __________________________________________________________
b) People have vaccines to provide protection against disease. Explain what a vaccine is.
c) The BCG vaccine is used against pulmonary heart disease. Scientists have been looking into a ‘booster’ vaccine called MVA85A which has been created to increase the immune response of the original vaccine, BCG. The memory T cells of three groups was carried out:
Group A was injected with only BCG
Group B was injected with only MVA85A
Group C was injected with BCG and then two weeks later with MVA85A

By the end of the experiment, group C came had produced the most T cells. What does this show about the two vaccines?

The body is made up of different cells, each of which have different functions.
a) White blood cells destroy bacteria. Some are phagocytic. How do phagocytic white blood cells carry out their role?
b) Name two areas in the body where white blood cells can be found.
i. _________________________________________________
ii. _________________________________________________

Monoclonal antibodies are created in vivo.
a) What is meant by the term in vivo?
b) Explain how monoclonal antibodies are created using mice?
c) Name two ethical issues some people have with monoclonal antibodies.
i. _________________________________________________
ii. _________________________________________________

ANSWERS

a)
i. Damage cells
ii. Produce toxins

b) A vaccine contains the antigen of a pathogen which is dead or weakened. When it’s injected into the body it stimulates the production of antibodies and memory cells.

c) They contained the same antigens.

a) Phagocytes attract bacteria by secreting chemicals. They recognise the pathogen by its foreign antigens. The phagocyte traps the pathogen in a phagosome which then fuses itself to a lysosome. The pathogen is hydrolysed by the lysozymes released into the phagosome by the lysosome.

b) Answers include:
i. blood
ii. tissue fluid
iii. lymph
iv. body cavities

a) Inside a living organism.

b) A mouse is injected with the antigen protein for which the antibodies are wanted. The mouse produces B-lymphocytes in its primary immune response. A few days later the B-lymphocytes are removed from the mouse’s blood. The blood contains a multitude of B-lymphocytes for different antigens so the right ones need to be isolated. To achieve this, the blood is diluted and injected into hundreds of wells within an immunoassay plate with one cell per well. The cells multiply and secrete their antibodies. The wells can then be tested to find the right antibodies and the B-cells grown to make millions of cloned cells, each producing the same antibodies known as monoclonal antibodies.

c) Answers include:
i. The production of monoclonal antibodies involves the use of live mice.
ii. The use of transgenic mice, which involves placing a human gene in a mouse, raises questions over the ethics of genetic engineering.
iii. Testing new drugs and vaccines on humans always carries risks.
iv. It’s important to know how effect a vaccine is throughout a population but testing it on vulnerable groups, like children, would raise concerns.