Unit 16 Question Bank

Immunoassay · agglutination, precipitation, ELISA, and the three practicals

16 MCQ3 Definitions5 Fill-in5 True/False2 Brief

The five tabs are the five sections of the real paper. Items tagged Past Paper 2019 or 2020 are the genuine questions, reproduced verbatim. Items tagged Slide come from the TMU lecture; items tagged Janeway's are built from the textbook to cover examinable ground. Nothing is invented. Janeway's 10e is a reflowed edition with no printed page numbers, so it is cited by numbered section (§1-14), not by page.

0 / 26 answered

1Direct agglutination is used to detect:

A. Antibody

B. Complement

C. Cytokines

D. Antigen

Answer: D

Direct agglutination detects antigen — the antigen is already on a particle such as a red cell, so adding known antibody clumps it. ABO blood typing is the standard example. Indirect agglutination detects antibody, by first coating soluble antigen onto latex particles.TMU Lecture 12 — Immunoassay (Yu Chunyan) Slide 18

2The rheumatoid factor test and the pregnancy test are examples of:

A. Indirect agglutination

B. Direct agglutination

C. Single immunodiffusion

D. Rocket electrophoresis

Answer: A

Both detect something in the patient's sample using an artificially coated particle. The pregnancy test is specifically an indirect agglutination inhibition test for hCG, read with a colloidal-gold signature.TMU Lecture 12 — Immunoassay (Yu Chunyan) Slides 18, 22

3Agglutination is best defined as:

A. Interaction of soluble antigen with antibody giving a precipitin line

B. Interaction of insoluble particulate antigen with specific antibody giving visible agglutinates

C. Enzymatic conversion of substrate to a coloured product

D. Lysis of target cells by complement

Answer: B

The antigen must be particulate — intact bacteria or cells — and the result appears after a certain time and at a certain electrolyte concentration. Soluble antigen gives precipitation instead.TMU Lecture 12 — Immunoassay (Yu Chunyan) Slide 19

4Which is a quantitative precipitation method?

A. Direct agglutination

B. E-rosette test

C. Rocket electrophoresis

D. Lymphocyte transformation test

Answer: C

Rocket electrophoresis and single immunodiffusion are quantitative precipitation methods. The E-rosette and transformation tests assess cells, not antigen or antibody concentration.TMU Lecture 12 — Immunoassay (Yu Chunyan) Slide 26

5ELISA generates its signal by means of:

A. A radioisotope emitting gamma radiation

B. Visible clumping of latex particles

C. Direct lysis of indicator red cells

D. An enzyme conjugated to antibody, producing a colour change with its substrate

Answer: D

Enzyme-Linked ImmunoSorbent Assay. It is quantitative, sensitive and can be run on many samples at once — which is why it is used for hormone assays and infectious serology alike, and why it is one of your three assessed practicals.TMU Lecture 12 — Immunoassay (Yu Chunyan) — ELISA practical

6A patient allergic to pollen, dust mites, seafood and peanuts — which antibody and cytokine are mainly involved?

A. IgE and IL-4

B. IgG and IFN-γ

C. IgM and IL-2

D. IgA and TGF-β

Answer: A

This is the lecture's own question. IgE mediates type I hypersensitivity, and IL-4 from Th2 cells drives the class switch that produces it. Both are measured by ELISA.TMU Lecture 12 — Immunoassay (Yu Chunyan) Slide 15

7The neutralization practical demonstrates:

A. Complement lysing antibody-coated red cells

B. Tetanus antitoxin blocking the activity of tetanus exotoxin

C. PHA transforming lymphocytes into lymphoblasts

D. Agglutination of latex particles by rheumatoid factor

Answer: B

Neutralisation is the one antibody function requiring neither complement nor cells — which is why pepsin-digested F(ab′)₂ antitoxin still works despite having no Fc.TMU Lecture 12 — Immunoassay (Yu Chunyan) Slide 12

8The lymphocyte transformation test uses which stimulus, over what period?

A. Antigen-specific peptide, over 30 minutes

B. Complement, over 1 hour

C. PHA, over 48–72 hours

D. Colloidal gold, over 5 minutes

Answer: C

PHA is a polyclonal T-cell mitogen (Unit 2), converting small resting lymphocytes into lymphoblasts. The test measures T-cell function rather than number.TMU Lecture 12 — Immunoassay (Yu Chunyan) Slide 11

9The E-rosette test identifies T cells because:

A. CD3 binds sheep red cell membranes

B. T cells agglutinate spontaneously

C. CD4 binds MHC class II on erythrocytes

D. CD2 is the receptor for sheep erythrocytes

Answer: D

CD2 (LFA-2) is stated in the T-cell lecture as the sheep erythrocyte receptor — the E receptor. The assay is an application of a fact from Unit 7.TMU Lecture 12 — Immunoassay (Yu Chunyan) Slide 11 · Unit 7 Slide 124

10Immune cells are evaluated along which two axes?

A. Number and function

B. Size and shape

C. Antibody titre and complement level

D. MHC class I and class II expression

Answer: A

A patient can have a normal lymphocyte count and profoundly defective function — which is exactly why both must be measured, and why a negative tuberculin test (Unit 15) can indicate immunodeficiency rather than absence of exposure.TMU Lecture 12 — Immunoassay (Yu Chunyan) Slide 10

11The nude mouse is used in immunology experiments because it:

A. Lacks B cells and cannot make antibody

B. Is congenitally athymic and therefore lacks mature T cells

C. Has no complement system

D. Cannot express MHC class I

Answer: B

No thymus means no T-cell maturation — the living proof of what the thymus does (Unit 1). Such mice cannot reject skin grafts, which is why they are used to grow human tumour xenografts.TMU Lecture 12 — Immunoassay (Yu Chunyan) Slide 13

12What is the final goal of immunoassay?

A. Production of therapeutic antibody

B. Induction of immune tolerance

C. Clinical diagnosis, therapy assessment, prognosis and scientific research

D. Vaccination against infectious disease

Answer: C

Immunoassay is a measuring discipline. Producing therapeutic antibody and vaccinating belong to immunotherapy (Unit 17).TMU Lecture 12 — Immunoassay (Yu Chunyan) Slide 15

13According to this lecturer's stated exam structure, which section appears that is absent from both the 2019 and 2020 papers?

A. A 12-mark true/false section

B. A picture-labelling section

C. A 30-mark essay section

D. A 10-mark MULTIPLE-choice (multi-answer) section

Answer: D

⚠️ Slide 3 lists: 6 definitions (18), 56 blanks at 0.5 each (28), 20 single choices (20), 10 multiple choices (10), and 4 brief answers (24). Both past papers instead have 20 blanks, a 12-mark true/false section and five brief answers. Prepare the content, not the format.TMU Lecture 12 — Immunoassay (Yu Chunyan) Slide 3

14What proportion of the course mark comes from the experiments?

A. 30%

B. 10%

C. 50%

D. 70%

Answer: A

Experiments 30%, final examination 70% (Lecture 1, slide 2). The three practicals — ELISA, neutralization, and observation of immune organs — are therefore worth nearly a third of the subject.TMU Lecture 1 Slide 2

15Which method would you use to determine the serum concentration of allergen-specific IgE?

A. Direct agglutination

B. ELISA

C. Double immunodiffusion

D. E-rosette test

Answer: B

ELISA is quantitative and sensitive enough for IgE, which is present only in trace amounts (Unit 3). The alternative clinical approach is the skin test, which detects IgE already bound to skin mast cells rather than free in serum.TMU Lecture 12 — Immunoassay (Yu Chunyan) Slide 58 · Unit 13

16In indirect agglutination, soluble antigen must first be:

A. Digested with pepsin

B. Conjugated to an enzyme

C. Coated onto a carrier particle such as latex

D. Denatured by heating to 56 °C

Answer: C

Soluble antigen cannot clump visibly on its own, so it is attached to an artificial particle; patient antibody then cross-links those particles into visible aggregates. The chemistry is identical to direct agglutination — only the reagent supplied and the target sought are swapped.TMU Lecture 12 — Immunoassay (Yu Chunyan) Slides 18, 25

1 Agglutination — 3 marks+

The interaction of insoluble particulate antigens — intact bacteria or cells — with specific antibodies, resulting in visible agglutinates after a certain time and under a certain electrolyte concentration. Direct agglutination detects antigen (ABO blood typing); indirect agglutination detects antibody (rheumatoid factor, pregnancy test).TMU Lecture 12 — Immunoassay (Yu Chunyan) Slides 18–19

2 ELISA — 3 marks+

Enzyme-Linked ImmunoSorbent Assay — a labelled immunoassay in which an enzyme conjugated to antibody converts a substrate to a coloured product, so the amount of antigen or antibody present can be measured. Quantitative, sensitive and suitable for many samples at once; used clinically for allergen-specific IgE, hormone assay and infectious serology.TMU Lecture 12 — Immunoassay (Yu Chunyan) — ELISA practical

3 Goals and scope of immunoassay — 3 marks+

All immunoassay rests on the specific binding of antigen and antibody. Methods may be qualitative (detecting the existence of antigen or antibody) or quantitative (detecting concentration), and visible or invisible (requiring a label). Immunodetection covers both antigen/antibody and lymphocytes. The final goal is clinical diagnosis, therapy assessment, prognosis and scientific research.TMU Lecture 12 — Immunoassay (Yu Chunyan) Slides 14–17

1 ? agglutination detects antigen, as in ABO blood typing; ? agglutination detects antibody, as in the rheumatoid factor test.2 mark(s)

The chemistry is the same; only the reagent supplied and the target sought are swapped.

TMU Lecture 12 — Immunoassay (Yu Chunyan) Slide 18

2In an allergic patient the antibody mainly involved is ? and the cytokine is ? ; both can be measured by ? .3 mark(s)

The lecture poses this as its own question. IL-4 from Th2 drives the class switch to IgE.

TMU Lecture 12 — Immunoassay (Yu Chunyan) Slide 15

3The lymphocyte transformation test uses ? stimulation over ? hours; the E-rosette test works because ? is the sheep-erythrocyte receptor.3 mark(s)

Both assays are applications of facts from Units 2 and 7 — mitogens, and the CD2 E receptor.

TMU Lecture 12 — Immunoassay (Yu Chunyan) Slide 11

4Immune cells are evaluated by their ? and their ? .2 mark(s)

A normal count can conceal defective function — which is why a negative tuberculin test may mean immunodeficiency rather than no exposure.

TMU Lecture 12 — Immunoassay (Yu Chunyan) Slide 10

5The final goals of immunoassay are ? , ? , ? and ? .4 mark(s)

Immunoassay measures; immunotherapy treats.

TMU Lecture 12 — Immunoassay (Yu Chunyan) Slide 15

1Direct agglutination is used to detect antibody in a patient's serum.

FALSE

False — direct agglutination detects antigen, as in ABO blood typing, where known anti-A and anti-B sera identify the antigen on the patient's red cells. Indirect agglutination detects antibody.TMU Lecture 12 — Immunoassay (Yu Chunyan) Slide 18

2All immunoassays rest on the specific binding of antigen and antibody.

TRUE

True. Every technique in the unit is a way of making that invisible binding event visible and then countable — by clumping, precipitating, or attaching a label that generates a signal.TMU Lecture 12 — Immunoassay (Yu Chunyan) Slide 14

3A normal lymphocyte count guarantees normal lymphocyte function.

FALSE

False — which is precisely why immune cells are evaluated on two separate axes, number and function. Functional tests such as the lymphocyte transformation test exist for exactly this reason.TMU Lecture 12 — Immunoassay (Yu Chunyan) Slide 10

4The exam structure stated in this lecture matches the 2019 and 2020 past papers.

FALSE

FALSE — and this matters. Slide 3 gives 6 definitions (18), 56 blanks at 0.5 each (28), 20 single choices (20), 10 MULTIPLE choices (10) and 4 brief answers (24). The past papers instead have 20 blanks, a 12-mark true/false section, and five brief answers. A multi-answer MCQ section appears in neither past paper. Prepare the content, not the format.TMU Lecture 12 — Immunoassay (Yu Chunyan) Slide 3

5The nude mouse lacks a thymus and therefore cannot produce mature T cells.

TRUE

True, and it is the living demonstration of Unit 1's claim about the thymus. Such mice cannot reject skin grafts, which is why they are used to grow human tumour xenografts.TMU Lecture 12 — Immunoassay (Yu Chunyan) Slide 13

1 Describe the methods available for detecting antigen and antibody. 6 marks

Principle. All rest on the specific binding of antigen and antibody. Methods may be qualitative (existence) or quantitative (concentration), and visible or invisible (needing a label).

Method	Detail
Agglutination	Insoluble particulate antigen + specific antibody → visible agglutinates. Direct (detects antigen) — ABO blood typing. Indirect (detects antibody) — rheumatoid factor; pregnancy test by indirect agglutination inhibition for hCG
Precipitation	Soluble antigen + antibody. Single immunodiffusion and rocket electrophoresis are quantitative; double immunodiffusion is qualitative
Labelled immunoassay	ELISA — enzyme conjugated to antibody, substrate gives a colour change; quantitative and sensitive. Also fluorescent, radioisotope and colloidal-gold labels

The organising question for any assay: if you supply known antibody you are hunting antigen; if you supply known antigen you are hunting antibody.

Marking guide: 2 marks per method group. Distinguishing direct from indirect agglutination by what each detects is the most commonly examined point.

2 How are immune cells evaluated? 6 marks

Immune cells are assessed along two axes: number (normal range, higher, lower) and function (normal, stronger, deficient). Both are needed, because a normal count can conceal defective function.

Test	Measures
Lymphocyte transformation test	T-cell function — PHA stimulation converts small lymphocytes into lymphoblasts over 48–72 hours
E-rosette test	T cells — CD2 is the sheep-erythrocyte receptor
Phagocytosis assay	Phagocyte function
Skin test / OT test	Type I hypersensitivity (30 min) or cell-mediated immunity (24–48 h)

The clinical importance of the function axis is shown by the tuberculin test: a negative result may mean no exposure — or that the patient is immunodeficient and cannot mount the response at all.

Marking guide: 2 marks for the number/function framework, 1 per named test with what it measures.