Question 19M.2.SL.TZ1.g
| Date | May 2019 | Marks available | [Maximum mark: 3] | Reference code | 19M.2.SL.TZ1.g |
| Level | SL | Paper | 2 | Time zone | TZ1 |
| Command term | Explain | Question number | g | Adapted from | N/A |
Explain how vaccination can lead to the production of B cells specific to the Ebola virus.
[3]
a. vaccine contains Ebola antigens ✔
b. vaccine «could» contain weakened/attenuated/dead/killed form of «Ebola» virus/virus genetically modified to express an Ebola/viral protein ✔
c. phagocyte/macrophage engulfs the antigen/presents the antigen to T cell ✔
d. antigen recognized by «specific» T cells/binds to T cells ✔
e. «activated» T cells activate «specific) B cells ✔
f. «activated» B cells make the antibodies «against Ebola» ✔
g. B cells divide forming «clone of» plasma cells/producing more B cells specific to Ebola ✔
This was a timely question with Ebola epidemics again causing great problems in parts of Africa. Students were expected to have had some practice at analysing data relating to an epidemic because of this Skill in the programme: Analysis of epidemiological data related to vaccination programmes. It was assumed that candidates would understand terms such as ‘case’, ‘fatal case’, ‘infect’ and ‘treat’.
Vaccination is a major focus on 11.1 of the programme so it was perhaps surprising that answers here were not better. Given the current outbreaks of measles and other diseases that can be prevented by vaccination, this topic should be given greater prominence in some schools. There were a few impressive answers giving the details of the steps that lead up to production of antibodies against a specific pathogen, but less than a quarter of candidates scored all three marks. There were many misconceptions. The terms ‘resistant’ and ‘immune’ have different meanings in biology, which should be carefully distinguished. Some candidates think that a vaccine contains a small amount of the pathogen. Would those candidates be happy to be infected with Ebola viruses as long as it was only a few? There was too much talk of cells ‘remembering’ the antigen or the virus. Memory cell is perhaps an unfortunate term. They are only memory cells in the sense that if an antigen binds to the antibodies they display, after cell multiplication more of those antibodies are produced and they will bind to the same antigens on the surface of an invading pathogen. This is just a series of molecular processes, not true memory.
