Unit 6 Question Bank
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 / 28 answered
1CD molecules are so named because they:
Answer: A
Cluster of differentiation records the observation that surface markers change as a cell matures — a molecule may be present on an immature cell and gone from the mature one. That is exactly why a CD panel tells a haematologist both the lineage and the developmental stage of a leukaemic cell.TMU Lecture 6 — CDs and CAMs Slide 4
2CD molecules are defined and identified by means of:
Answer: B
Monoclonal antibodies. The whole numbering system exists because the hybridoma technique let many laboratories raise antibodies against the same surfaces; antibodies recognising one molecule were grouped into a numbered cluster so everyone could mean the same thing.TMU Lecture 6 — CDs and CAMs Slide 4
3Which CD molecule is the signal-transduction element of the T-cell receptor?
Answer: C
CD3 is part of the TCR complex itself and is therefore present on all T cells — which is why it identifies T lineage. CD4 and CD8 then divide T cells into helper and cytotoxic; CD28 is the co-stimulatory receptor.TMU Lecture 6 — CDs and CAMs Slide 6
4Which CD molecule is the receptor for B7?
Answer: D
CD28 on the T cell binds B7 (CD80/CD86) on the antigen-presenting cell — the co-stimulatory second signal. CTLA-4 binds the same ligands with higher affinity but delivers an inhibitory signal, which is MCQ Q16 in Unit 7.TMU Lecture 6 — CDs and CAMs Slides 6, 14
5Which CD molecule is the receptor for complement C3d and for Epstein–Barr virus?
Answer: A
CD21 (complement receptor 2, CR2). It is part of the B-cell co-receptor complex with CD19 and CD81 — and being the EBV receptor explains why that virus infects B cells. CD35 is CR1, the C3b receptor; CD32 is an IgG Fc receptor.TMU Lecture 6 — CDs and CAMs Slide 6 · Janeway's Immunobiology 10e on CR2
6CD16 is a low-affinity receptor for the Fc region of IgG. On which cells is it principally expressed?
Answer: B
NK cells, macrophages and neutrophils. On NK cells CD16 (FcγRIII) triggers ADCC; on phagocytes it drives uptake of antibody-coated pathogens. ⚠️ Note: the deck's printed table appears to place CD16 on B cells — that is a typesetting/extraction artefact. The B-cell IgG Fc receptor is CD32.Janeway's Immunobiology 10e on CD16/FcγRIII — correcting the deck's garbled table
7Which CD molecule is the leukocyte common antigen, present on B cells, Th cells, Tc cells and NK cells alike?
Answer: C
CD45. Because it is on every leukocyte it identifies a cell as a leukocyte but tells you nothing else — in a marker panel it functions as the control. CD2 is on T and NK cells; CD56 is the classic NK marker.TMU Lecture 6 — CDs and CAMs Slide 6
8Cell adhesion molecules are grouped into how many protein families, and which?
Answer: D
Four families, and the order is nearly the order of use in the adhesion cascade: selectins bind mucin-like carbohydrate to start rolling, then integrins bind Ig-superfamily CAMs for firm adhesion.TMU Lecture 6 — CDs and CAMs Slide 8
9Which adhesion family initiates the leukocyte–endothelial interaction?
Answer: A
Selectins. They bind carbohydrate, so the bonds form and break rapidly — the cell slows and rolls rather than stopping dead, which a firm bond at full flow velocity would not survive. Integrins then provide the strong adhesion that actually arrests the cell.TMU Lecture 6 — CDs and CAMs Slide 9
10L-selectin, E-selectin and P-selectin are expressed respectively on:
Answer: B
The initial letters give it away — L for leukocyte, E for endothelium, P for platelet. P-selectin is also stored preformed in endothelial Weibel–Palade bodies, which is why it reaches the surface within minutes of activation by TNF-α.TMU Lecture 6 — CDs and CAMs Slide 9 · Janeway's Immunobiology 10e
11Integrins are:
Answer: C
α/β heterodimers giving strong adhesion, binding Ig-superfamily CAMs and the extracellular matrix. Heavily glycosylated proteins presenting carbohydrate are the mucins; Ig-like domains define the Ig superfamily.TMU Lecture 6 — CDs and CAMs Slide 12
12ICAM-1, ICAM-2, ICAM-3 and VCAM-1 belong to which CAM family?
Answer: D
They contain Ig-like domains — the same Ig fold met in Unit 3, which also builds TCR, MHC, CD4, CD8 and B7. They are usually expressed on vascular endothelial cells and are the ligands that activated integrins grip during firm adhesion.TMU Lecture 6 — CDs and CAMs Slide 11
13Which CAMs act as co-stimulators in the immune response?
Answer: A
CD28 with CD80/CD86 (B7) supply the co-stimulatory second signal for T-cell activation. CD4 and CD8 are the co-receptors — they grip MHC and hold the contact while the TCR reads the peptide. Both roles are CAM functions, but the question asks for the co-stimulators.TMU Lecture 6 — CDs and CAMs Slide 14
14Place the steps of leukocyte extravasation in the correct order.
Answer: B
Selectins tether and roll; chemokines displayed on the endothelium then activate the leukocyte's integrins to a high-affinity state; the integrins bind ICAM-1 and VCAM-1 for firm adhesion; and the cell finally squeezes between endothelial cells — diapedesis. Weak-and-quick first, strong-and-lasting second.Janeway's Immunobiology 10e §3-19 · TMU Lecture 6 — CDs and CAMs Slide 15
15A child has recurrent bacterial infections, a very high circulating neutrophil count, wounds that produce no pus, and delayed separation of the umbilical cord. The defect is in:
Answer: C
Neutrophils are made normally — hence the high blood count — but cannot complete firm adhesion, so they never leave the vessel. Pus is neutrophils in tissue, so there is none; and umbilical cord separation depends on neutrophil infiltration, so it is delayed. Terminal complement deficiency causes recurrent Neisseria infection instead.Janeway's Immunobiology 10e — Case Study: Leukocyte Adhesion Deficiency
16The tissue-side ligand recognised by a lymphocyte homing receptor is called:
Answer: D
The lymphocyte homing receptor (LHR) sits on the lymphocyte; the addressin is the tissue-specific ligand it reads — the tissue is displaying its address. Naïve T cells home to secondary lymphoid tissue; effector T cells home to mucosa or skin depending on where they were activated.TMU Lecture 6 — CDs and CAMs Slides 14, 16 · Janeway's Immunobiology 10e
1 CD (cluster of differentiation) — 3 marks+
A series of membrane molecules or markers determined by monoclonal antibodies. They are called clusters of differentiation because these molecules appear or disappear at different stages of cell differentiation and maturation. Numbering currently runs from CD1 to CD247, organised into 13 groups — CD molecules of T cells, B cells, NK cells, platelets, adhesion molecules and others.TMU Lecture 6 — CDs and CAMs Slides 4–5
2 CAM (cell adhesion molecule) — 3 marks+
A group of cell-surface molecules that mediate adhesive interactions with other cells or with the extracellular matrix, playing crucial roles in cell migration and cellular activation in immune responses. There are four protein families: selectin, mucin-like, immunoglobulin superfamily and integrin.TMU Lecture 6 — CDs and CAMs Slide 8
3 Selectins — 3 marks+
Membrane glycoproteins that bind carbohydrate ligands, typically presented by mucin-like CAMs. Their function is to initiate the leukocyte–endothelial interaction — the bonds form and break rapidly, producing rolling rather than arrest. Three types: L-selectin on leukocytes, E-selectin on endothelial cells, P-selectin on platelets.TMU Lecture 6 — CDs and CAMs Slide 9
4 Integrins — 3 marks+
Heterodimeric proteins consisting of an α and a β chain, which bind CAMs (often of the Ig superfamily) and the extracellular matrix, and provide strong adhesion. They must first be activated — typically by chemokine signalling — to reach their high-affinity state.TMU Lecture 6 — CDs and CAMs Slide 12
5 Immunoglobulin superfamily CAMs — 3 marks+
Adhesion molecules containing a variable number of immunoglobulin-like domains, including ICAM-1, ICAM-2, ICAM-3 and VCAM-1. They are usually expressed on vascular endothelial cells and bind various integrin molecules.TMU Lecture 6 — CDs and CAMs Slide 11
6 Lymphocyte homing receptor and addressin — 3 marks+
CAMs that direct lymphocyte homing — the routine circulation of lymphocytes to particular tissues. The lymphocyte homing receptor (LHR) is carried by the lymphocyte; the addressin is the tissue-specific ligand it recognises. Naïve T cells home to secondary lymphoid tissues; effector T cells home to mucosal or skin sites according to where they were activated.TMU Lecture 6 — CDs and CAMs Slides 14, 16
1CD is short for ? of ? , so named because these molecules appear or disappear at different stages of cell ? and ? .4 mark(s)
The name records the observation, not the function — which is why a CD panel reports both a cell's lineage and its developmental stage.
TMU Lecture 6 — CDs and CAMs Slide 42The four families of cell adhesion molecules are ? , ? , ? and ? .4 mark(s)
Learn them in this order — it is nearly the order in which they are used during leukocyte extravasation: selectin binds mucin to start rolling, then integrin binds Ig-superfamily CAM for firm adhesion.
TMU Lecture 6 — CDs and CAMs Slide 83L-selectin is expressed on ? , E-selectin on ? , and P-selectin on ? .3 mark(s)
The initial letters carry the answer. P-selectin is additionally stored preformed in endothelial Weibel–Palade bodies, so it appears on the surface within minutes of TNF-α activation.
TMU Lecture 6 — CDs and CAMs Slide 94Integrins are heterodimers composed of an ? chain and a ? chain, and mediate ? adhesion.3 mark(s)
Contrast selectins, whose carbohydrate binding is deliberately weak and transient so that the cell rolls rather than being torn away by the flow.
TMU Lecture 6 — CDs and CAMs Slide 125The three general functions of CAMs are acting as ? and ? in the immune response, mediating leukocyte ? and inflammation, and directing lymphocyte ? .4 mark(s)
Co-receptors are CD4 and CD8; co-stimulators are CD28, CD80 and CD86. Each of the three functions is developed in a later unit.
TMU Lecture 6 — CDs and CAMs Slide 146The four steps by which a leukocyte leaves a blood vessel are ? , ? of integrins by chemokines, ? adhesion, and ? .4 mark(s)
All four CAM families appear in order: selectin → mucin (rolling), then integrin → Ig superfamily (firm adhesion). The one non-adhesion step is done by a cytokine.
Janeway's Immunobiology 10e §3-191CD molecules are identified using monoclonal antibodies.
TRUE
True — and this is why the system exists. Once hybridomas made monoclonal antibodies easy to produce, many laboratories were naming the same surface molecules differently; grouping antibodies into numbered clusters solved it.TMU Lecture 6 — CDs and CAMs Slide 4
2CD16 is expressed on B lymphocytes.
FALSE
False. CD16 (FcγRIII) is on NK cells, macrophages and neutrophils, where it mediates ADCC and the uptake of antibody-coated pathogens. The B-cell IgG Fc receptor is CD32. ⚠️ The deck's printed table appears to show CD16 under B cells; that is a typesetting artefact and is corrected here against Janeway's.Janeway's Immunobiology 10e on CD16/FcγRIII
3Integrins initiate the first contact between a rolling leukocyte and the endothelium.
FALSE
False — that is the selectins. Integrins act later, and only after chemokine signalling has switched them to a high-affinity state; they provide the firm adhesion that arrests the cell. A strong bond formed at full flow velocity would tear, which is why the weak carbohydrate bond has to come first.TMU Lecture 6 — CDs and CAMs Slides 9, 12
4CD4 and CD8 function as co-receptors and are also adhesion molecules.
TRUE
True, and the two descriptions are the same fact from two angles: CD4 and CD8 grip the MHC molecule on the antigen-presenting cell and hold the contact together while the TCR reads the peptide. The lineage marker is the adhesion function.TMU Lecture 6 — CDs and CAMs Slides 6, 14
5Naïve T cells home preferentially to skin and mucosal sites.
FALSE
False. Naïve T cells home to secondary lymphoid tissues, where antigen is brought to them — there would be no point sending a cell that has never met its antigen to a particular tissue. Only after activation do effector T cells acquire receptors for mucosal or cutaneous addressins.TMU Lecture 6 — CDs and CAMs Slide 16
6In leukocyte adhesion deficiency the circulating neutrophil count is characteristically low.
FALSE
False — it is characteristically high. The neutrophils are produced normally but cannot adhere firmly and so cannot leave the vessel, accumulating in the blood instead. The same mechanism explains the absence of pus and the delayed umbilical cord separation.Janeway's Immunobiology 10e — Case Study: Leukocyte Adhesion Deficiency
1
What are CD molecules, and what are they used for?
6 marks
Definition. CD stands for cluster of differentiation — a series of membrane molecules or markers determined by monoclonal antibodies. They are so named because these molecules appear or disappear at different stages of cell differentiation and maturation.
Scale. Numbered CD1–CD247, organised into 13 groups (T cell, B cell, NK cell, platelet, adhesion molecules, and others).
Uses. ① Identifying cell lineage and developmental stage — the basis of immunophenotyping in leukaemia and lymphoma. ② Many CD molecules have defined functions: CD3 transduces the TCR signal; CD4 and CD8 are co-receptors; CD28 receives B7; CD40 receives the B-cell second signal; CD21 is the C3d and EBV receptor; CD16 mediates ADCC.
Marking guide: 2 marks for the definition including the reason for the name, 1 for the numbering/groups, 3 for uses with named examples.
2
Describe the four families of cell adhesion molecules.
6 marks
| Family | Structure | Binds | Role |
|---|---|---|---|
| Selectin | Membrane glycoproteins | Carbohydrate on mucin-like CAMs | Initiates leukocyte–endothelial interaction; L on leukocytes, E on endothelium, P on platelets |
| Mucin-like | Heavily glycosylated proteins | Selectins | Extended structure presents carbohydrate ligands to selectins |
| Ig superfamily | Contain Ig-like domains | Integrins | ICAM-1, ICAM-2, ICAM-3, VCAM-1; on vascular endothelium |
| Integrin | α/β heterodimers | Ig-superfamily CAMs and extracellular matrix | Strong adhesion |
Worth adding: selectin–carbohydrate binding is deliberately weak and rapidly reversible, producing rolling; integrin binding is strong and stable, producing arrest. The two-stage design exists because a firm bond formed at full flow velocity would tear.
Marking guide: 1.5 marks per family. Full marks require naming the members (L/E/P selectins; ICAM/VCAM) and stating which family initiates and which gives strong adhesion.
3
Describe the general functions of cell adhesion molecules.
6 marks
① Co-receptors and co-stimulators in the immune response. Some CAMs act as co-receptors — CD4 and CD8, which grip MHC and stabilise the contact while the TCR reads peptide. Others act as co-stimulators — CD28, CD80 and CD86 — supplying the second signal for T-cell activation.
② Leukocyte migration and inflammation. Extravasation proceeds in four steps: rolling (selectins binding mucin-like carbohydrate) → activation of integrins by chemokines displayed on the endothelium → firm adhesion (integrins binding ICAM-1 and VCAM-1) → transmigration. Endothelium is licensed for this by TNF-α, which externalises preformed P-selectin.
③ Lymphocyte homing. Mediated by lymphocyte homing receptors (LHR) on the lymphocyte and addressins on the tissue. Naïve T cells home to secondary lymphoid tissue; effector T cells home to mucosal or skin sites according to where they were activated.
Marking guide: 2 marks per function. The migration answer must give the steps in order to earn full credit; naming CD4/CD8 and CD28/B7 secures the first.