New: our faculty are still reviewing these cards. Spotted an error? Use “Report an issue” on the card in the app, or contact us.

Immunology flashcards

15 high-yield MRCP Part 1 cards from the Intellect Medicos Basic sciences & statistics course. Try to answer each question before you open it — then study them properly with spaced repetition, which brings each card back just before you would forget it.

Study these 15 cards Save progress — free account

1. Deficiency of which complement components predisposes to recurrent Neisseria infections?

   Show answer

   The terminal components C5-C9 (membrane attack complex).

   Why? Neisseria are killed mainly by complement-mediated lysis via the membrane attack complex.

2. A 24-year-old has recurrent episodes of non-itchy swelling of the lips and abdominal pain, with no urticaria and no response to antihistamines. Her father has similar episodes. What is the best initial screening blood test?

   Show answer

   Serum C4 (low), followed by C1-inhibitor level and function.

   Why? Hereditary angioedema (autosomal dominant C1-inhibitor deficiency) causes uncontrolled complement activation that consumes C4.

3. Which blood test supports a diagnosis of anaphylaxis after the event?

   Show answer

   Serum mast cell tryptase (timed samples).

   Why? Tryptase is released from degranulating mast cells in type I (IgE-mediated) hypersensitivity and peaks within a few hours.

4. What is the first-line treatment for anaphylaxis in an adult, including dose and route?

   Show answer

   IM adrenaline 500 micrograms (0.5 mL of 1 in 1000) into the anterolateral thigh, repeated after 5 minutes if needed.

   Why? Adrenaline reverses vasodilatation and bronchospasm and stops further mast cell mediator release.

5. What is the first-line investigation for suspected allergic contact dermatitis?

   Show answer

   Patch testing.

   Why? Allergic contact dermatitis is a type IV (T-cell-mediated, delayed) hypersensitivity reaction, so the reaction is read 48-72 hours after applying the allergen.

6. What is the recommended first-line laboratory test for HIV infection in the UK?

   Show answer

   A fourth-generation combined HIV antibody and p24 antigen immunoassay; a reactive result is confirmed on a second assay.

   Why? Including p24 antigen shortens the window period compared with antibody-only tests.

7. Which immunoglobulin class crosses the placenta to give the newborn passive immunity?

   Show answer

   IgG (the only class that crosses).

   Why? IgG is actively transported across the placenta. This is also why maternal anti-D (IgG) causes haemolytic disease of the newborn, whereas naturally occurring ABO antibodies are mainly IgM and do not cross.

8. A man with recurrent sinus and chest infections has an anaphylactic reaction during his first blood transfusion. What is the most likely underlying immune defect?

   Show answer

   Selective IgA deficiency (his anti-IgA antibodies react with IgA in the donor blood).

   Why? IgA deficiency is the commonest primary antibody deficiency; IgA protects mucosal surfaces.

9. In the complement cascade, ______ is the main opsonin, and C5a is the main chemoattractant for neutrophils.

   Show answer

   C3b

   Why? C3 is shared by the classical, lectin and alternative pathways; C5b then starts the membrane attack complex (C5b-9).

10. In the complement cascade, C3b is the main opsonin, and ______ is the main chemoattractant for neutrophils.

    Show answer

    C5a

    Why? C3 is shared by the classical, lectin and alternative pathways; C5b then starts the membrane attack complex (C5b-9).

11. What is the treatment of an acute attack of hereditary angioedema?

    Show answer

    C1-esterase inhibitor concentrate, or icatibant (a bradykinin B2 receptor antagonist).

    Why? The swelling is driven by bradykinin, not histamine.

12. Which Gell and Coombs type is Goodpasture's (anti-GBM) disease, and what is the target antigen?

    Show answer

    Type II (antibody against a fixed tissue antigen); the target is type IV collagen in glomerular and alveolar basement membranes.

    Why? Antibody binding activates complement and recruits neutrophils, causing rapidly progressive glomerulonephritis and lung haemorrhage.

13. ______ drives eosinophil growth and activation, and IL-4 drives B-cell class switching to IgE.

    Show answer

    IL-5

    Why? Both come from Th2 cells, which coordinate responses to parasites and allergy.

14. IL-5 drives eosinophil growth and activation, and ______ drives B-cell class switching to IgE.

    Show answer

    IL-4

    Why? Both come from Th2 cells, which coordinate responses to parasites and allergy.

15. Which test is used to screen for chronic granulomatous disease?

    Show answer

    The dihydrorhodamine (DHR) flow cytometry test (which has replaced the nitroblue tetrazolium test).

    Why? An NADPH oxidase defect stops neutrophils making the respiratory burst, giving recurrent catalase-positive infections (e.g. Staphylococcus aureus, Aspergillus) and granulomas.