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Question 1
Correct
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Which of the following immunoglobulins is most important for mast cell degranulation:
Your Answer: IgE
Explanation:IgA is the major Ig in secretions, particularly from the gastrointestinal tract (but also in saliva, tears, sweat and breast milk).
IgE is important for mast cell degranulation in allergic and antiparasitic response. In the allergic response, the plasma cell produces IgE-antibodies, which, like antibodies of other immunoglobulin isotypes, are capable of binding a specific allergen via its Fab portion.
IgG is the most abundant in plasma (comprising 80% of normal serum immunoglobulin) and the main circulatory Ig for the secondary immune response. -
This question is part of the following fields:
- Immune Responses
- Pathology
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Question 2
Correct
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Which of the following best describes the process of opsonisation:
Your Answer: The coating of foreign particles with molecules which allow easier recognition of that cell by phagocytes
Explanation:An opsonin is any molecule that enhances phagocytosis by marking an antigen for an immune response, for example, immunoglobulin or complement. Opsonisation is the molecular mechanism whereby molecules, microbes, or apoptotic cells are chemically modified to have a stronger attraction to the cell surface receptors on phagocytes and natural killer cells. With the antigen coated in opsonins, binding to immune cells is greatly enhanced. Opsonisation also mediates phagocytosis via signal cascades from cell surface receptors.
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This question is part of the following fields:
- Immune Responses
- Pathology
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Question 3
Correct
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In all of the following conditions, lymphocytosis typically occurs except for:
Your Answer: Corticosteroid therapy
Explanation:In infants and young children, lymphocytosis often occurs in response to infections that would normally produce a neutrophil reaction in adults.
Lymphocytosis occurs in:
1. Viral infections (e.g. infectious mononucleosis, HIV, rubella, mumps, viral hepatitis, cytomegalovirus, herpes simplex or zoster)
2. Bacterial infections (e.g. pertussis, tuberculosis, toxoplasmosis, syphilis)
3. Chronic lymphoid leukaemias
4. Acute lymphoblastic leukaemias
5. Non-Hodgkin lymphoma
6. Thyrotoxicosis -
This question is part of the following fields:
- Immune Responses
- Pathology
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Question 4
Correct
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Which of the following is NOT typically associated with eosinophilia:
Your Answer: Whooping cough
Explanation:An eosinophil leucocytosis is defined as an increase in blood eosinophils above 0.4 x 109/L.It is most frequently due to:
Allergic diseases (e.g. bronchial asthma, hay fever, atopic dermatitis, urticaria)
Parasites (e.g. hookworm, ascariasis, tapeworm, schistosomiasis)
Skin diseases (e.g. psoriasis, pemphigus, urticaria, angioedema)
Drug sensitivity -
This question is part of the following fields:
- Immune Responses
- Pathology
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Question 5
Correct
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The following are all examples of type I hypersensitivity EXCEPT for:
Your Answer: Contact dermatitis
Explanation:Examples of type I reactions include:
Allergic rhinitis
Allergic conjunctivitis
Allergic asthma
Systemic anaphylaxis
Angioedema
Urticaria
Penicillin allergy -
This question is part of the following fields:
- Immune Responses
- Pathology
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Question 6
Incorrect
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The following are all examples of type III hypersensitivity EXCEPT for:
Your Answer: Extrinsic allergic alveolitis
Correct Answer: Goodpasture's syndrome
Explanation:Examples of type III reactions include:
Extrinsic allergic alveolitis
Systemic lupus erythematosus (SLE)
Post-streptococcal glomerulonephritis
Reactive arthritis
Rheumatoid arthritis -
This question is part of the following fields:
- Immune Responses
- Pathology
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Question 7
Correct
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Which of the following does NOT typically cause a neutrophil leucocytosis:
Your Answer: Glandular fever
Explanation:Causes of neutrophil leucocytosis:
Bacterial infection
Inflammation and tissue necrosis (e.g. cardiac infarct, trauma, vasculitis, myositis)
Metabolic disorders (e.g. uraemia, acidosis, eclampsia, gout)
Pregnancy
Acute haemorrhage or haemolysis
Neoplasms of all types
Drugs (e.g. corticosteroid therapy, lithium, tetracyclines)
Asplenia
Myeloproliferative disorders (e.g. CML, essential thrombocythaemia, polycythaemia vera, myelofibrosis)
Rare inherited disorders -
This question is part of the following fields:
- Immune Responses
- Pathology
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Question 8
Correct
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Which of the following statements about neutrophils is TRUE:
Your Answer: Neutrophils are typically the first immune cell to arrive to a site of injury.
Explanation:Neutrophils are the most numerous peripheral blood leukocytes, accounting for 50-70 percent of all circulating white cells. Neutrophils have a compact nucleus with two to five lobes and a pale cytoplasm with an irregular shape containing numerous fine pink-blue or grey-blue granules. The granules are classified as primary, which emerges during the promyelocyte stage, and secondary, which develop at the myelocyte stage and predominate in the mature nucleus.
The lifespan of neutrophils in the blood is only 6 – 10 hours. In response to tissue damage, cytokines and complement proteins, neutrophils migrate from the bloodstream to the site of insult within minutes, where they destroy pathogens by phagocytosis.
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This question is part of the following fields:
- Immune Responses
- Pathology
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Question 9
Correct
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Regarding cytotoxic T cells, which of the following statements is CORRECT:
Your Answer: They kill target cells by inducing cell apoptosis.
Explanation:CD8+ T-cells (Cytotoxic T cells)
Recognise antigen only in association with HLA Class I molecules (found on all nucleated cells; present endogenous antigens such as those found in cells infected by viruses or intracellular bacteria.)
Comprise about 25% of peripheral T-cells
Responsible for cytotoxic killing of target cells -
This question is part of the following fields:
- Immune Responses
- Pathology
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Question 10
Correct
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Which of the following best describes a natural killer cell:
Your Answer: A large granular lymphocyte that kills by inducing target cell apoptosis.
Explanation:Natural killer (NK) cells are cytotoxic CD8 positive cells that lack the T-cell receptor. They are large cells with cytoplasmic granules. NK cells are designed to kill target cells that have a low level of expression of HLA class I molecules, such as may occur during viral infection or on a malignant cell. NK cells do this by displaying several receptors for HLA molecules on their surface. When HLA is expressed on the target cell these deliver an inhibitory signal into the NK cell. When HLA molecules are absent on the target cell this inhibitory signal is lost and the NK cell can then kill its target. In addition, NK cells display antibody-dependent cell-mediated cytotoxicity. In this, antibody binds to antigen on the surface of the target cell and then NK cells bind to the Fc portion of the bound antibody and kill the target cell.
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This question is part of the following fields:
- Immune Responses
- Pathology
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Question 11
Correct
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The most important Complement protein for antigen opsonization is:
Your Answer: C3b
Explanation:Phagocytosis is largely responsible for depletion of cells coated with antibodies. Cells opsonized by IgG antibodies are recognized by phagocyte Fc receptors, which are specific for the Fc portions of some IgG subclasses. In addition, when IgM or IgG antibodies are deposited on the surfaces of cells, they may activate the complement system by the classical pathway. Complement activation generates by-products, mainly C3b and C4b, which are deposited on the surfaces of the cells and recognized by phagocytes that express receptors for these proteins. The net result is phagocytosis of the opsonized cells and their destruction.
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This question is part of the following fields:
- Immune Responses
- Pathology
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Question 12
Correct
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You are giving a presentation on the immune system as part of your peer-to-peer teaching sessions. Yu are currently discussing phagocytes. Macrophages are derived from which of the following cells:
Your Answer: Monocytes
Explanation:Monocytes spend only a short time in the marrow and, after circulating for 20-40 hours, leave the blood to enter the tissues where they become macrophages. Macrophages form the reticuloendothelial system in the liver, spleen and lymph nodes. The lifespan of macrophages may be as long as several months or even years. In tissues the macrophages become self-replicating without replenishment from the blood. They assume specific functions in different tissues e.g. dendritic cells which are involved in antigen presentation to T-cells. Macrophages may be activated by cytokines such as IFN-gamma, contact with complement or direct contact with the target cell through leucocyte adhesion molecules.
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This question is part of the following fields:
- Immune Responses
- Pathology
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Question 13
Correct
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Which of the following is NOT a function of antibodies:
Your Answer: Act as antigen receptors on T lymphocytes
Explanation:Antibodies:
Neutralise toxins and prevent attachment of pathogens
Target, opsonise or agglutinate (clump together) antigens for phagocytosis
Activate the complement cascade (leading to lysis or opsonisation of the pathogen)
Act as antigen receptors on B lymphocytes
Activate antibody-dependent cell-mediated cytotoxicity by natural killer (NK) cells or T cytotoxic cells
Provide mucosal immunity (IgA-mediated)
Stimulate degranulation of mast cells (IgE and IgG mediated)
Provide passive immunity to the newborn (through transplacental passage of IgG and secretion of IgA in breast milk) -
This question is part of the following fields:
- Immune Responses
- Pathology
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Question 14
Correct
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Which of the following laboratory findings are suggestive of functional hyposplenism:
Your Answer: Howell-Jolly bodies
Explanation:Functional hyposplenism is characterised by the blood film findings of Howell-Jolly bodies or siderotic granules on iron staining. The most frequent cause is surgical removal of the spleen e.g. after traumatic rupture, but hyposplenism can also occur in sickle cell anaemia, gluten-induced enteropathy, amyloidosis and other conditions.
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This question is part of the following fields:
- Immune Responses
- Pathology
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Question 15
Correct
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Approximately what proportion of lymphocytes are B-cells:
Your Answer: 0.2
Explanation:B-cells (20% of lymphocytes) mature in the bone marrow and circulate in the peripheral blood until they undergo recognition of antigen. B-cell immunoglobulin molecules synthesised in the cell are exported and bound to the surface membrane to become the B-cell receptor (BCR) which can recognise and bind to a specific antigen (either free or presented by APCs). The BCR is also important for antigen internalisation, processing and presentation to T helper cells. Most antibody responses require help from antigen-specific T helper cells (although some antigens such as polysaccharide can lead to T-cell independent B-cell antibody production). When the B-cell is activated, the receptor itself is secreted as free soluble immunoglobulin and the B-cell matures into a memory B-cell or a plasma cell (a B-cell in its high-rate immunoglobulin secreting state). Plasma cells are non-motile and are found predominantly in the bone marrow or spleen. Most plasma cells are short-lived (1 – 2 weeks) but some may survive much longer. A proportion of B-cells persist as memory cells, whose increased number and rapid response underlies the augmented secondary response of the adaptive immune system.
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This question is part of the following fields:
- Immune Responses
- Pathology
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Question 16
Correct
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Which of the following statements is correct with regards to immunoglobulin?
Your Answer: The isotype of immunoglobulin is determined by the heavy chain.
Explanation:The composition of immunoglobulin molecules is two identical heavy and two identical light chains. These chains are linked by disulphide bridges and are each have highly variable regions which give the immunoglobulin its specificity. In addition, they have constant regions and there is virtual complete correspondence in amino acid sequence in all antibodies of a given isotype.
Five isotypes of immunoglobulin exist – these are IgG, IgA, IgM, IgE and IgD. They are determined by the heavy chain (gamma, alpha, mu, epsilon or delta respectively). The light chains are either kappa or lambda. -
This question is part of the following fields:
- Immune Responses
- Pathology
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Question 17
Correct
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A 22-year-old man arrives at the emergency department with a sore throat, low-grade fever, and malaise. His partner has infectious mononucleosis, which was recently diagnosed. In this situation, which of the following cells is the most proliferative:
Your Answer: Lymphocytes
Explanation:Histologic findings in EBV infectious mononucleosis: Oropharyngeal epithelium demonstrates an intense lymphoproliferative response in the cells of the oropharynx. The lymph nodes and spleen show lymphocytic infiltration primarily in the periphery of a lymph node.
Relative lymphocytosis (≥ 60%) plus atypical lymphocytosis (≥ 10%) are the characteristic findings of Epstein Barr virus (EBV) infectious mononucleosis. -
This question is part of the following fields:
- Immune Responses
- Pathology
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Question 18
Correct
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Regarding basophils, which of the following statements is INCORRECT:
Your Answer: They are the second most common type of granulocyte.
Explanation:Basophils are only occasionally seen in normal peripheral blood comprising < 1% of circulating white cells. However, they are the largest type of granulocyte. They have many dark cytoplasmic granules which overlie the nucleus and contain heparin and histamine. They have immunoglobulin E (IgE) attachment sites and their degranulation is associated with histamine release. Basophils are very similar in both appearance and function to mast cells.
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This question is part of the following fields:
- Immune Responses
- Pathology
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Question 19
Correct
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Which of the following is the most abundant peripheral blood leucocyte:
Your Answer: Neutrophils
Explanation:Neutrophils are the most abundant peripheral blood leucocyte, comprising about 50 – 70% of circulating white cells. Neutrophils have a characteristic dense nucleus consisting of between two and five lobes, and a pale cytoplasm with an irregular outline containing many fine pink-blue or grey-blue granules. The granules are divided into primary, which appear at the promyelocyte stage, and secondary, which appear at the myelocyte stage and predominate in the mature nucleus. Both types of granule are lysosomal in origin; the primary contains myeloperoxidase and other acid hydrolases; the secondary contains lactoferrin, lysozyme and other enzymes. The lifespan of neutrophils in the blood is only 6 – 10 hours. In response to tissue damage, cytokines and complement proteins, neutrophils migrate from the bloodstream to the site of insult within minutes, where they destroy pathogens by phagocytosis.
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This question is part of the following fields:
- Immune Responses
- Pathology
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Question 20
Correct
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In which of the following would you NOT typically see a neutropaenia:
Your Answer: Asplenism
Explanation:Causes of neutropaenia:
Drug-induced (e.g. chemotherapy, chloramphenicol, co-trimoxazole, phenytoin, carbamazepine, carbimazole, furosemide, chloroquine, clozapine, some DMARDs)
Benign (racial or familial)
Cyclical
Immune (e.g. SLE, Felty’s syndrome, hypersensitivity and anaphylaxis)
Leukaemia
Infections (e.g. HIV, hepatitis, fulminant bacterial infection)
General Pancytopaenia
Hypersplenism, aplastic anaemia, malignant infiltration of bone marrow, megaloblastic anaemia, chemotherapy, myelodysplasia -
This question is part of the following fields:
- Immune Responses
- Pathology
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Question 21
Correct
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Which of the following statements is correct with regards to natural killer cells?
Your Answer: They are part of the innate immune system.
Explanation:Natural Killer (NK) Cells are lymphocytes in the same family as T and B cells, which come from a common progenitor. They are cytotoxic CD8 positive cells that do not have the T-cell receptor. They are very big cells with cytoplasmic granules and are designed to kill target cells with a low level of expression of HLA class I molecules.
Examples include during a viral infection or on a malignant cell. NK cells display several receptors for HLA molecules on their surface, and when HLA is expressed on the target cell, these deliver an inhibitory signal into the NK cell. Absent HLA molecules on the target cell cause this inhibitory signal to get lost and as a result, the NK cell can then kill its target. Also, NK cells display antibody-dependent cell-mediated cytotoxicity, where antibody binds to antigen on the surface of the target cell. The NK cells then bind to the Fc portion of the bound antibody and kill the target cell. -
This question is part of the following fields:
- Immune Responses
- Pathology
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Question 22
Correct
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Question 23
Correct
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Regarding T helper cells, which of the following statements is CORRECT:
Your Answer: They form the vast majority (about 75%) of the total circulating T-cell population.
Explanation:CD4+ T-cells (Helper T cells)Recognise antigen only in association with HLA class II molecules (found on antigen presenting cells (APCs) e.g. dendritic cells, B-cells; present exogenous antigens that have been phagocytosed/endocytosed into intracellular vesicles)Form most of the circulating T-cell population (about 75%)Secrete cytokines (e.g. IFN-gamma) which are required for recruitment and activation of other immune cells such as macrophages, T cytotoxic cells and NK cells and for the activation of and production of immunoglobulin from B-cells
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This question is part of the following fields:
- Immune Responses
- Pathology
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Question 24
Correct
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Mast cells play a significant part in which of the following?
Your Answer: Allergic disease
Explanation:Mast cells play a central role in the response to allergen challenges. The activation of mast cells results in both an early and a delayed phase of inflammation. Mast cells have been implicated in both physiologic and pathogenic processes. Mast cells are important in defence against some bacteria and viruses and contribute to defence against parasites. They are key effector cells in both innate and acquired immunity and are capable of inducing and amplifying both types of responses. Specifically, mast cells are capable of detecting microbial products through surface pattern recognition receptors, and they are involved in the recruitment of other leukocytes, containment of bacterial infections, and tissue repair.
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This question is part of the following fields:
- Immune Responses
- Pathology
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Question 25
Correct
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Question 26
Correct
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Which of the following immunoglobulin molecules is the most abundant in secretions (such as saliva and breast milk):
Your Answer: IgA
Explanation:IgA is the predominant antibody class in secretions and tremendous quantities are secreted into various body spaces and onto mucosal surfaces (the gut lumen, the pharynx and sinuses, the larger airways, although not the alveoli).
Because of its size, the majority of IgM is found in the circulation.Along with IgM, IgD is predominant among the surface receptors of mature B cells, where it plays a key role in B cells activation.
IgE has the lowest concentration in normal human serum. It plays a prominent role in immune responses to helminth parasites, and in allergic reactions.
IgG is the most abundant immunoglobulin and constitutes 75 percent of serum immunoglobulin in an adult human -
This question is part of the following fields:
- Immune Responses
- Pathology
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Question 27
Correct
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Which of these immunoglobulin molecules can cross the placenta?
Your Answer: IgG
Explanation:An important mechanism that provides protection to the foetus is placental transfer of maternal IgG antibodies while his/her humoral response is inefficient. The only antibody class that significantly crosses the human placenta is IgG.
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This question is part of the following fields:
- Immune Responses
- Pathology
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Question 28
Incorrect
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The following are all examples of type II hypersensitivity EXCEPT for:
Your Answer: Goodpasture's syndrome
Correct Answer: Post-streptococcal glomerulonephritis
Explanation:Examples of type II reactions include:
Incompatible blood transfusions
Haemolytic disease of the newborn
Autoimmune haemolytic anaemias
Goodpasture’s syndrome
Rheumatic heart disease
Bullous pemphigoid -
This question is part of the following fields:
- Immune Responses
- Pathology
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Question 29
Correct
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Eosinophils comprise what percentage of circulating white cells:
Your Answer: 1 - 3%
Explanation:Eosinophils comprise 1 – 3% of circulating white cells. Eosinophils are similar to neutrophils, except that the cytoplasmic granules are coarser and more deeply red staining, and there are rarely more than three nuclear lobes. They are less motile, but longer lived. They enter inflammatory exudates and have a special role in allergic responses, defence against parasites and removal of fibrin formed during inflammation. Thus they play a role in local immunity and tissue repair.
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This question is part of the following fields:
- Immune Responses
- Pathology
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Question 30
Incorrect
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The following are all examples of type IV hypersensitivity EXCEPT for:
Your Answer: Contact dermatitis
Correct Answer: Extrinsic allergic alveolitis
Explanation:Examples of type IV reactions includes:
Contact dermatitis
Hashimoto’s thyroiditis
Primary biliary cholangitis
Tuberculin skin test (Mantoux test)
Chronic transplant rejection
Granulomatous inflammation (e.g. sarcoidosis, Crohn’s disease) -
This question is part of the following fields:
- Immune Responses
- Pathology
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SESSION STATS - PERFORMANCE PER SPECIALTY
