Clinical Immunology MCQs- Practice Questions

Clinical Immunology MCQs: The Practice Questions You Actually Need

You need to pass your immunology exam. You don't need a 500-page textbook summary. This is a collection of high-yield practice questions that cover the real exam material. No fluff, no padding—just the questions and answers that matter.

If you're studying for USMLE, PLAB, or any clinical immunology exam, these MCQs will show you where you stand. Work through them. Check your answers. Fix your gaps.

Why Clinical Immunology MCQs Are Non-Negotiable

Reading notes doesn't test your knowledge. It just shows you recognize the words. MCQs force you to actively recall information under pressure—which is exactly what happens during your exam.

Most students fail because they:

• Read passively and think they've learned
• Avoid practice questions until the last minute
• Don't review explanations for wrong answers

Don't be that student. Start practicing now.

Core Topics in Clinical Immunology

These questions cover the topics that appear most often on exams:

• Primary immunodeficiencies — PIDD patterns, genetic causes, clinical presentations
• Hypersensitivity reactions — Type I-IV mechanisms and examples
• Autoimmune disorders — SLE, RA, autoimmune hepatitis
• Immunoglobulin structure and function — Classes, subclasses, Fc receptors
• Complement system — Pathways, deficiencies, regulators
• Transplant immunology — HLA matching, rejection types, immunosuppression
• Vaccines and immunotherapy — Mechanisms, schedules, monoclonal antibodies

Practice Questions: Test Yourself

Read each question. Pick your answer before moving to the next. No peeking.

Question 1

A 3-year-old boy presents with recurrent sinopulmonary infections, normal lymphocyte counts, and low serum IgG, IgA, and IgE. T-cell function is normal. What is the most likely diagnosis?

A) DiGeorge Syndrome
B) Common Variable Immunodeficiency (CVID)
C) X-linked Agammaglobulinemia (Bruton's)
D) Severe Combined Immunodeficiency (SCID)

Answer: C

X-linked agammaglobulinemia presents in boys after 6 months (when maternal antibodies wane) with recurrent bacterial infections and absent mature B cells. All immunoglobulin classes are low. T-cells are normal. CVID typically presents later (after age 4) and can affect both sexes.

Question 2

Which complement deficiency is most associated with recurrent Neisseria infections?

A) C1q deficiency
B) C3 deficiency
C) C5-9 terminal pathway deficiency
D) C1 inhibitor deficiency

Answer: C

C5 through C9 form the membrane attack complex (MAC). Deficiency in any terminal component causes susceptibility to Neisseria meningitidis and Neisseria gonorrhoeae. These bacteria have thin cell walls that specifically require MAC for lysis. C1 inhibitor deficiency causes hereditary angioedema instead.

Question 3

A patient with systemic lupus erythematosus (SLE) has antibodies to double-stranded DNA. Which antibody is most specific for this diagnosis?

A) ANA
B) Anti-Smith
C) Anti-dsDNA
D) Anti-histone

Answer: C

Anti-double-stranded DNA antibodies are specific for SLE (specificity ~95%). Anti-Smith antibodies are also specific but less sensitive. ANA is sensitive but not specific—it appears in many autoimmune conditions and even healthy individuals. Anti-histone is associated with drug-induced lupus.

Question 4

A Type I hypersensitivity reaction is mediated by:

A) IgG and complement
B) IgE and mast cells
C) T-cells and macrophages
D) Immune complexes and neutrophils

Answer: B

Type I (immediate) hypersensitivity involves IgE bound to mast cell FcεRI receptors. Cross-linking by allergen triggers mast cell degranulation, releasing histamine, leukotrienes, and prostaglandins. Think allergies, asthma, anaphylaxis. Type II involves antibodies against cell surfaces. Type III involves immune complexes. Type IV is T-cell mediated (delayed).

Question 5

Which HLA class I molecule is most associated with ankylosing spondylitis?

A) HLA-B27
B) HLA-DR4
C) HLA-DR3
D) HLA-A2

Answer: A

HLA-B27 is strongly linked to spondyloarthropathies including ankylosing spondylitis, reactive arthritis, and psoriatic arthritis. >90% of patients with ankylosing spondylitis are HLA-B27 positive. HLA-DR4 is associated with rheumatoid arthritis and type 1 diabetes. HLA-DR3 is linked to SLE, type 1 diabetes, and myasthenia gravis.

Question 6

A patient with chronic granulomatous disease (CGD) has recurrent infections with catalase-positive organisms. Which organism is the classic cause of infection in CGD?

A) Streptococcus pneumoniae
B) Staphylococcus aureus
C) Haemophilus influenzae
D) Neisseria meningitidis

Answer: B

CGD results from defective NADPH oxidase, preventing respiratory burst and superoxide production. Patients get infections with catalase-positive organisms because these bacteria destroy any H2O2 they produce themselves. Staphylococcus aureus, Burkholderia cepacia, Serratia marcescens, and Nocardia are classic. The nitroblue tetrazolium (NBT) test is diagnostic.

Question 7

Which immunoglobulin crosses the placenta?

A) IgM
B) IgG
C) IgA
D) IgE

Answer: B

Only IgG crosses the placenta via the FcRn receptor. This provides passive immunity to the fetus. IgM is too large. IgA in secretory form doesn't cross—it's in breast milk via a different mechanism. IgE doesn't cross. This is why IgM antibodies in the newborn suggest intrauterine infection (they can't cross the placenta).

Question 8

A transplant recipient develops acute kidney dysfunction 2 weeks post-renal transplant. Biopsy shows interstitial infiltration with lymphocytes and tubular damage. What type of rejection is this?

A) Hyperacute rejection
B) Acute cellular rejection
C) Acute humoral rejection
D) Chronic rejection

Answer: B

Acute cellular rejection occurs days to weeks after transplant and is mediated by recipient T-cells attacking donor MHC. It shows lymphocytic infiltration on biopsy. Hyperacute rejection occurs within minutes (preformed antibodies). Chronic rejection takes months to years with vascular changes and fibrosis. Acute humoral rejection involves antibody-mediated vascular damage.

Quick Reference: Immunodeficiency Patterns

How to Use These Clinical Immunology MCQs

Don't just read through them. Here's what actually works:

1. Take the test blind — No peeking at answers. Write down your choices.
2. Grade yourself strictly — Wrong is wrong. Partial credit doesn't exist on exam day.
3. Read every explanation — Even for questions you got right. You might have guessed.
4. Identify your weak areas — Go back to your notes or textbook for those topics only.
5. Repeat after 48 hours — Spaced repetition beats massed practice every time.
6. Time yourself — Build speed. Most exams don't give you unlimited time.

Best Resources for More Clinical Immunology MCQs

What You Should Know Before Your Exam

Immunology questions on clinical exams almost always test the same concepts:

• Know the hypersensitivity types — Mechanisms, examples, and which antibodies or cells are involved
• Know the immunodeficiency patterns — Which cells are affected, what infections result
• Know HLA associations — B27 with spondyloarthropathies, DR3 and DR4 with autoimmune diseases
• Know complement pathways — Classical, lectin, alternative. Terminal pathway deficiencies and infections
• Know immunoglobulin classes — Which crosses placenta, which is in secretions, which activates complement

That's it. These are the patterns. Once you recognize them, the questions become predictable.

Final Word

Don't waste time memorizing every detail of cytokine pathways or obscure enzyme deficiencies. Focus on high-yield patterns. Practice questions expose those patterns faster than any other study method.

Use these MCQs. Review what you missed. Repeat until you're consistently scoring above 80%. Then you're ready.