DMF MSE 2 2007

1

Which one of the following statements about antibody gene rearrangement is correct?


  Antibody gene rearrangement predominantly involves CH genes

  Antibody gene rearrangement selects for high affinity antibodies

  Antibody gene rearrangement only occurs after antigen stimulation

  Antibody gene rearrangement is required to create functional antibody genes

  Antibody gene rearrangement requires T cell help

2

Which one of the following statements about HLA molecules is correct?


  HLA molecules generate receptor diversity by gene rearrangement

  HLA polymorphism affects antigen recognition by T cells

  HLA molecules undergo somatic hypermutation

  Mature T cells bind HLA molecules with very high affinity

  HLA Class II molecules are expressed by almost all nucleated cells

3

The activation of T and B cells is the central process of the adaptive immune system. Which one of the statements below correctly describes features in the activation process which are shared by both T and B cells?


  Many different antigens may activate individual T or B cells

  Both T and B cell receptors only recognise antigens derived from pathogens

  Both T and B cells are activated in infected tissues

  Antigen processing by both dendritic cells and macrophages activates both T and B cells

  Both T and B cells circulate through lymphoid tissues where they encounter antigen

4

Which one of the statements below concerning antigen presenting cells is correct?


  Antigen presenting cells may influence the differentiation pathway of T helper cells they are activating

  Class I and Class II MHC molecules associated with antigen presenting cells predominantly bind foreign peptides

  Antigen presenting cells display antigens which are derived exclusively from the cytosol on MHC Class II antigens

  Activated antigen presenting cells are retained in infected tissues to defend against invading pathogens

  The co-stimulatory molecules CD80 and CD86 are constitutively expressed on antigen presenting cells

5

CD8 Cytotoxic T cells and Natural Killer (NK) cells possess several shared characteristics. Select the characteristic described below which is not shared by both cell types


  Cytotoxic T cells and NK cells kill their target cells using perforin and granzymes

  Individual cytotoxic T cells and NK cells bind Class I MHC molecules on target cells

  Individual cytotoxic T cells and NK cells kill cells infected by several different viruses

  Activated cytotoxic T cells and NK cells can secrete interferon gamma

  Cytotoxic T cells and NK cells do not kill uninfected target cells

6

Which one of the following statements about the pathogenesis of diseases caused by immune responses is incorrect?


  Systemic lupus erythematosis (SLE) is characterised by deposition of antigen – antibody complexes in synovium, small blood vessels and glomeruli

  Antibodies against nuclear antigens may contribute significantly to the pathogenesis of SLE

  Antibodies against gliadin may contribute significantly to the pathogenesis of coeliac disease

  Animal models of insulin dependent diabetes mellitis (IDDM) suggest that islet cell damage is due to a destructive T cell response

  Infections of particular tissues may result in the expression of costimulatory molecules on antigen presenting cells leading to the breakdown of T cell tolerance to self antigens

7

Which one of the following statements below is regarding clonal anergy?


  Encounter with antigen during T cell differentiation in the thymus typically results in clonal anergy

  Clonal anergy involves a state of non-responsiveness to specific antigen by lymphocytes

  Clonal anergy involves ignorance of antigen by specific T lymphocytes

  Clonal anergy involves malignant transformation of aberrant lymphocytes

  Clonal anergy involves specific apoptosis of self-reactive T cells

8

Which one of the following statements about immediate (Type I) hypersensitivity reactions is correct?


  Individuals who are atopic will display the symptoms of Type I hypersensitivity immediately after their first exposure to a particular allergen

  Type I hypersensitivity reactions are predominantly mediated by IgE which is secreted by plasma cells in response to interferon gamma stimulation

  Type I hypersensitivity reactions are predominantly mediated by degranulation of mast cells which have bound complement and allergen

  Type I hypersensitivity reactions are predominantly mediated by crosslinking of IgE bound FcRε on the surface of mast cells by allergen

  Type I hypersensitivity reactions are predominantly mediated by complexes of IgE and antigen which form in submucosal tissues and subsequently bind mast cells

9

Which one of the following statements about mast cells is incorrect?


  Mast cells contain histamine that is rapidly released upon degranulation.

  Mast cells bind IgE through high affinity cell surface receptors.

  Mast cells make and release cysteinyl leukotrienes.

  Mast cells are targets for the anti-allergic actions of anti-histamines.

  Mast cells are targets for anti-allergic actions of disodium cromoglycate.

10

Which one of the following statements about vaccines is correct?


  An advantage of inactivated vaccines is that they produce a longer-lived response than live attenuated vaccines do

  MMR vaccine is safe to use in immunocompromised individuals

  A conjugated vaccine is one where different polysaccharide antigens from related organisms are chemically linked together

  The hepatitis B vaccine is a live attenuated vaccine

  The efficacy of immunisation with a live attenuated viral vaccine may be compromised by the presence of circulating antibodies

11

Tania Plotkin, a sixteen year old girl, was investigated for an immune deficiency because of a history of recurrent infections.

On investigation, her levels of immunoglobulins and complement components were normal. Assays for antibodies to vaccine antigens showed normal levels of antibodies to these antigens. Her neutrophil numbers and function were also normal.

Tania’s T cell numbers, as determined by measuring the number of cells expressing CD3, were found to be normal. B cell numbers were also normal and they expressed MHC Class II antigens. However, Tania’s lymphocytes and other nucleated cells did not express MHC Class I antigens.

Which one of the following would be consistent with these laboratory data?


  Tania’s lymphocytes are normal in number and function

  Tania would be likely to be unable to control infections with capsulated bacteria

  Tania would be likely to be deficient in helper T cells

  Tania’s helper T cells would be unable to secrete gamma-interferon

  Tania would be likely to be deficient in cytotoxic T cells

12

Which one of the following statements concerning increased vascular permeability associated with acute inflammation is incorrect?


  Oedema first develops in acute inflammation due to the formation of a high protein transudate (Specific Gravity > 1.020)

  An immediate, sustained increase in permeability is likely to be mediated by direct endothelial cell injury

  Histamine release is likely to produce an immediate, transient pattern of increased permeability of post-capillary venules

  An immediate, transient pattern of increased permeability is likely to involve receptor-mediated contraction of endothelial cells

  A delayed increase in permeability may be mediated via cytokines such as TNF alpha

13

Which one of the following statements concerning cells associated with acute inflammation is incorrect?


  Neutrophils migrating into the tissues survive for only 4 to 6 hours

  Eosinophils contain histaminase which assists in terminating the acute inflammatory response

  Neutrophil myeloperoxidase helps to protect tissues from injury caused by peroxides released from activated phagocytes

  The immature neutrophils found in the circulation in association with an acute inflammatory response are known as "band forms"

  Complement component C5a is a chemotactic factor for neutrophils

14

One of the currently licensed vaccines against Streptococcus pneumoniae which is designed to induce protection against invasive pneumococcal disease is prepared from chemical conjugates of pneumococcal surface polysaccharides and a protein such as tetanus toxoid. Which one of the statements below correctly describes the features of this vaccine?


  It induces an immune response which targets all strains of Streptococcus pneumoniae

  It acts by eliciting antibodies that block the ability of pneumococcal polysaccharides to trigger the complement cascade

  Regular boosters (every 1 – 2 years) would be required to maintain the vaccine response

  It only induces immunity in adolescents and adults

  It induces isotype switching by antigen-activated B cells

15

A 17 year old girl presented to the emergency department of a teaching hospital with a one day history of headache, fever and photophobia. She had previously been well and had received all of her immunisations. CSF and blood cultures were collected and IV cefotaxime was administered. 45 minutes later the laboratory reported the following CSF results: 1140 leucocytes/μl (90% polymorphonuclear leukocytes); protein 2.0g per litre (normal < 0.4g/l); glucose 1.7mmol/l (normal ≥ 2.5 mmol/l); Gram negative diplococci seen on Gram stain; Latex agglutination tests for H. influenzae type b and Neisseria meningitidis were negative. On the basis of the test results, which one of the following infectious agents listed below is the most likely cause of her condition?


  Cryptococcus neoformans

  Neisseria meningitidis

  Mycobacterium tuberculosis

  Streptococcus pneumoniae

  Enterovirus

16

When confronted with an angry patient, which one of the following is least likely to be correct?


  It is never appropriate to end the interaction

  The anger usually reflects a severe personality problem in the patient

  Anger is never related to uncertainty or lack of information

  There are no limits to what is an acceptable level of aggression that can be expressed in a doctor patient interaction

  Angry outbursts usually have little emotional effect on professionals.

17

When managing a tearful patient which statement is least likely to be correct?


  The most common cause of crying is a mental illness

  Acknowledging the patient’s distress does not inevitably make it worse

  Resident doctors find tearful patient difficult to manage because they are unsure how to respond

  Communicating an understanding of the patient’s concerns may help alleviate distress in some cases

  A patient’s emotional distress may be related to the physical symptoms of their illness

18

When faced with a distressed family member, which statement is least likely to be correct?


  Dealing with a distressed family member is a role the treating doctor may undertake

  It is sometimes important to acknowledge when things have gone wrong

  The doctor should never express uncertainty about the prognosis

  Family members may have different concerns from that of the patient

  Distressed family members are usually angry with the medical care

19

Which one of the following changes will result in a significant fall in prevalence of gonorrhoea in a population with a high rate of gonorrhoea among heterosexuals?


  A 30% reduction in the mean number of sexual partners per year in this population (standard deviation remains constant)

  A significant increase in testing and treatment of women in the non core group

  A significant reduction in the number of sexual acts per sexual partnership

  Significantly greater access to sexual health services for the population

  The introduction of abstinence only before marriage campaign in schools in that community


Unsure if this is correct.

20

Which one of the following is least effective in reducing the prevalence of STIs (sexually transmissible infections)?


  Screening the non-core core group for STIs

  Developing a primary care focus on detecting and treating symptomatic patients.

  Testing for other STIs when a patient presents with one STI

  Screening partners of patients presenting with STIs

  Increasing the rate of condom use

21

The number of secondary infections that arise from one infectious case of a particular disease may be increased by which one of the following factors?


  Widespread use of an effective vaccine in the population.

  Treatment that controls the symptoms but not the excretion of the infectious agent

  Rapid progression of the disease from infection to severe illness

  A recent epidemic of the disease in the population

  Low population density

22

Which one of the following factors favours the eradication of an infectious disease of humans?


  Chronic human infections occur

  The infection is mainly a disease of animals

  Clinical illness is mild and indistinct

  The available vaccine is stable across a wide range of temperatures

  The causative organism forms spores in the natural environment