CMB2004/L01 Antibodies, T cell Receptors & MHC molecules

Question 1

Give 3 features of an effective immune response.

Answer 1

Recognise and respond to invading organisms
Not react to benign or self
Direct different effector mechanisms against different pathogens

Question 2

Give 3 features of specific/adaptive immunity.

Answer 2

Induced by exposure to infection
High specificity
Exhibits memory

Question 3

What is specific immunity mediated by? (2)

Answer 3

Lymphocytes (B/T cells)
Clonally distributed receptors

Question 4

Describe clonal selection theory. (3)

Answer 4

Diversity of B and T cells
Antigen encounter
Clonal expansion
Differentiation
Memory cells
Selection process

Question 5

How does the BCR (B cell receptor) aid immune response? (3)

Answer 5

Membrane form of Ig binds ‘free’ antigen
Secreted when B cell is activated
Now known as antibody

Question 6

How does the TCR (T cell receptor) aid immune response?

Answer 6

Recognises peptide fragment of antigen bound to MHC expressed by APC

Question 7

Give 2 roles of antibodies.

Answer 7

Activation of complement (opsonisation, classical pathway activation and MAC)
Activation of effector cells

Question 8

Describe the structure of an antibody. (2)

Answer 8

Paired variable (V) regions (H&L chains) form 2 identical antigen binding sites
Constant (C) regions responsible for structure and interaction

Question 9

What are the 2 types of light antibody chain?

Answer 9

Lambda and kappa

Question 10

What 2 components make up the antigen-binding site?

Answer 10

VH and VL

Question 11

Which part of the antibody determines the isotype/class?

Answer 11

Heavy chain (C region)

Question 12

How many domains do the antibody light and heavy chains have?

Answer 12

Light - 2 domains
Heavy - 4-5 domains

Question 13

What does each domain of an antibody consist of? (3)

Answer 13

110 amino acids
2 B sheets
Linked by disulphide bridge
Paired domains folded within protein

Question 14

How many hypervariable loops and regions are in an antibody?

Answer 14

Loops - 6
Regions HV1-3 (3 in VH and VL)

Question 15

What are the 2 kinds of epitopes?

Answer 15

Continuous
Conformational

Question 16

What is determined by CDRs?

Answer 16

Specificity and affinity of an antibody for Ag

Question 17

Describe the structure of a TCR.

Answer 17

Membrane-bound receptor
Smaller than BCR/antibody (4 Ig-like domains)
Heterodimer of a and B chain (sometimes y and d)

Question 18

What is the function of TCRs?

Answer 18

Recognise short peptide fragments (of Ags) bound to MHC molecules on other cells

Question 19

How do TCRs interact with antigens?

Answer 19

V domains interact with antigens
Each chain contributes 3 CDRs to Ag binding

Question 20

What kind of cells express MHC class I molecules?

Answer 20

Nearly all cell types

Question 21

What kind of cells express MHC class II molecules?

Answer 21

Restricted to a specialised group of immune cells

Question 22

What are the 3 kinds of MHC class I molecule?

Answer 22

HLA-A
HLA-B
HLA-C
Single (non-MHC located) gene encodes B2-microglobulin that associated

Question 23

Describe the structure of MHC class I molecules.

Answer 23

a1 & a2 domains fold to form B-sheet - peptide binding site
a3 domain/B2-microglobulin fold into Ig-like domains

Question 24

What are the 3 kinds of MHC class II molecules?

Answer 24

HLA-DP
HLA-DQ
HLA-DR
a and B chains encoded by separate genes encoded within MHC

Question 25

Describe the structure of MHC class II molecules.

Answer 25

Polymorphic a1 and B1 domains form peptide-binding site

Question 26

What is the role of the TCR expressed by a T cell that co-expresses CD8?

Answer 26

Binding MHC class I molecules

Question 27

What is the role of a T cell that co-expresses CD4?

Answer 27

Binding MHC class II molecules