Lecture 3

Question 1

3 main functions carried out by T cells

Answer 1

• Provide assistance to other cells in the immune system (Th cells)
• Limit excessive or undesired immune responses (Tregs)
• Kill infected cells (CTLs)

Question 2

Features of 𝛾𝛿-T cells

Answer 2

• Found in high numbers in mucosal tissues
• Form a large percentage of resident T cells
• Don’t have classical TCRs
• Important as first responders (express PRRs & produce cytokines)
• Not fully understood

Question 3

Main role of plasma cells

Answer 3

Produce lots of antibody specific to antigen

Question 4

How do T cells recognise antigen?

Answer 4

T cells recognise specific antigenic peptides that are presented by APCs bound to MHC molecules by the TCR on their surface

Question 5

MHC Class I molecules present antigens to __

Answer 5

CD8+ T cells

Question 6

MHC Class II molecules present antigens to __

Answer 6

CD4+ T cells

Question 7

What does CD28 on T cell surface recognise?

Answer 7

CD80 (B7-1) or CD86 (B7-2) on surface of APC

Question 8

CD3 is a co-receptor on T cell surface needed for __

Answer 8

signal transduction

Question 9

What is the antigen receptor on B cells?

Answer 9

a membrane-bound immunoglobulin (IgM or IgD)

Question 10

Major advantage that T cells have over B cells

Answer 10

T cells can inspect antigens that are largely confined within cells and are therefore inaccessible to Ig

Question 11

2 main parts of the antibody molecule

Answer 11

• Variable (Fab) region: Ag recognition
• Constant (Fc) region: effector function

Question 12

Can TCRs recognise free antigen?

Answer 12

No, but BCRs can recognise soluble Ag draining into the LN

Question 13

What happens when B cells clonally expand?

Answer 13

Differentiation into plamsa cells, which generate soluble Ab specific to that Ag

Question 14

What type of DC can ‘capture’ an Ag on its surface and present it to B cells in the lymph node?

Answer 14

follicular

Question 15

TCR and BCR specificity is generated through…

Answer 15

somatic recombination events

Question 16

What is encoded on the B cell surface by the B cell specific genes MB-1 and B29? What does it do?

Answer 16

Igα/Igβ heterodimer - associates with the membrane-spanning region of IgM µ chain

Question 17

What motifs on the BCR act as signal transducers through their ability to associate with and be phosphorylated by a series of tyrosine kinases?

Answer 17

Immunoreceptor tyrosine-based activation motifs (ITAMs)

Question 18

4 components of the B cell co-receptor complex

Answer 18

• CD19
• CD21/CR2 (enables complement to synergise with BCR)
• CD81/TAPA-1
• CD25

Question 19

B cell co-receptor complex synergises with the __ to __ B cells

Answer 19

BCR to activate B cells

Question 20

What is clonal selection? What does it ensure?

Answer 20

Ag activates lymphocyte with a complementary Ag receptor.
It ensures that only the relevant Ag-specific lymphocytes are triggered to produce the appropriate effector cells & memory cells.

Question 21

Where does clonal selection occur, and why?

Answer 21

in the secondary lymphoid organs (spleen, draining lymph nodes) - lymphoid tissues provide the best chance for a naive T cell to encounter an APC i.e. DC

Question 22

What pathway can the Fc region of Ab activate?

Answer 22

Classical complement pathway

Question 23

How do antibodies opsonise microbes for phagocytosis?

Answer 23

Directly via Fc receptors, indirectly via complement activation

Question 24

What do C3a and C5a do?

Answer 24

induce mast cell degranulation to release inflammatory mediators

Question 25

Role of C3b & C3d

Answer 25

opsonisation - engagement of complement receptors on phagocytes with complement proteins on microbe to induce phagocytosis

Question 26

What complement proteins form the membrane attack complex?

Answer 26

C5b-C9

Question 27

Which complement protein activates B cells?

Answer 27

C3d

Question 28

Role of C5a

Answer 28

Induce chemotaxis of neutrophils

Question 29

Complement activation increases chemotaxis, which leads to increased…

Answer 29

vascular permeability