Question

Question 3

Read the following three statements and then answer the question below.

• In 2019, the UK lost its ‘measles-free’ status.
• The basic reproduction number for measles (R0) is given as between 12 and 18, in different studies.
• The immunisation rate in the UK for measles dipped to a low point in 2003 to 80% coverage and since then has risen to 91% in 2019.

Question 5

1. Your friend is suffering from a fever and respiratory symptoms. She visits her GP and requests antibiotics. Explain why antibiotics may not be appropriate for her infection.
2. Describe the effects of the overuse of antibiotics on the bacterial population in humans.
3. In order to distinguish between viral and bacterial infections some GPs now use a rapid point-of-care (POC) test for levels of C-reactive protein (CRP). Explain the role of CRP in the immune response and its relevance to use in this test.
4. In a hospital setting, treatment with antibiotics is a risk factor for infection with Clostridium difficile. Explain why Clostridium difficile is commonly acquired in hospitals.

Explain, using calculations, the causal link between these three statements and briefly discuss whether there is any prospect of the UK regaining its ‘measles-free’ status in the next 5 years.

Question 6

1. The cytokine IFNγ is produced by Th1 cells. Outline three different functions of IFNγ in inflammation and/or the immune response.
2. Name one cytokine that is produced specifically by Th2 cells and state what effect it has on its target cell(s).
3. What advantage is there for the host in having two distinct patterns of immune response, controlled by Th1 and Th2 cells?

Answer 1

Question.5-

a. Antibiotics fight bacterial infections, but they won’t work against viral infections. That means they are not effective against the flu or the common cold. For example, symptoms such as a consistently high fever, nasal discharge and severe facial pain may indicate a bacterial sinus infection. Most sinus infections are viral, but if these symptoms linger for many days without improvement, the cause may indeed be bacterial one. The best way of treatment is not always antibiotics. Sometimes easing your symptoms while letting your body fight off a virus is the proper course of action.

b. The biggest problem with overusing antibiotics is bacteria adapts to that antibiotics. In simple words, bacteria become resistant to drugs over time, making it harder to treat them. In rare cases, this leads to deadly drug-resistant bacterial infections. Drug-resistant bacteria make it harder to find effective drug options when you do face a severe infection. When you are talking about large groups of people, this resistance can be dangerous, making it easier for an infection to spread.

c. C-reactive protein binds to phosphocholine on micro-organisms. It plays an important role in innate immunity as an early defence system against infections. Along with that, similar to immunoglobulin G, it activates complement, binds to Fc receptors and acts as an opsonin for various pathogens. This CRP in the point-of-care test can helps to reduce diagnostic uncertainty by differentiating between bacterial and viral infections. It has been shown to be cost-effective for reducing inappropriate antibiotic prescriptions.

d. Clostridium difficile is the most common cause of hospital-acquired infectious diarrhea in the developed world and has re-emerged in the recent years with apparent greater morbidity and mortality. It is transmitted via the fecal–oral route, although evidence of airborne spread is emerging. Clostridium difficile can be cultured from the stool of healthy adults, most people remain asymptomatic. Disruption of the gut flora, typically by antibiotics, allows C. difficile to proliferate, thus resulting in infection.

Question 6 -

a. Interferon-gamma can suppress the tumours by acting directly on tumour cells. It is done by inhibiting their proliferation while increasing MHC expression, antigen presentation and thus antigenicity and cell death. They act directly on the tumour cells by augmenting the function of tumour-infiltrating immune cells including TH1 cells, CTLs and macrophages, by suppressing the T-regulatory cells. It is a cytokine that plays an important role in inducing and modulating an array of immune responses. Cellular responses to IFN‐γ are mediated by its heterodimeric cell‐surface receptor (IFN‐γR), which activates the downstream signal transduction cascades, ultimately leading to the regulation of gene expression.

b. Th2 cells express a no.of cytokines that influence B-cell differentiation and antibody production, eosinophil recruitment, and mucus production. The main cytokines that are produced by Th2 cells are IL-4, IL-5, and IL-13. Th2 cells can also produce IL-9, IL-10, IL-25, and amphiregulin. If we take IL-4 here, it is a cytokine that functions as a potent regulator of immunity secreted primarily by mast cells, Th2 cells, eosinophils and basophils. Along the other actions, STAT6 promotes transcription of GATA-3 and MHC-II and induces Ig-E class switching in B-cells.