Session 7 - adaptive immunity part 2

Question 1

Impaired thymus development will affect the function of which lymphocytes?

Answer 1

T-cells and B-cells

B-cells are activated by T cells

Question 2

What is the TCR made up of?

Answer 2

• T Cell Receptor: 2 chains (alpha and beta)
• CD3 complex co-receptor
  (4 chains)
• accessory molecule CD4/8

Question 3

What are the three signals which fully activate the naïve T lymphocyte?

Answer 3

1) TCR binding antigen in MHC
2) CD28 binding B7 on APC
3) cytokines from APC

Question 4

Following activation, the naïve T cell differentiates into 1 of 4 types of T helper cell.
Name the types

Which one has an inhibitory effect on another?

Answer 4

TH1
TH2
TH17
T reg

T reg inhibits TH1 and TH2 to help regulate the immune system

Question 5

Which T helper cell is most useful against intracellular pathogens?
What does it do?

Answer 5

TH1

• stimulates CD8+ cytotoxic cell differentiation
• produces cytokines which activate and recruit macrophages
• Induces class switching to IgG or IgA

Question 6

What does TH17 do?

Answer 6

recruits and activates neutrophils

Question 7

Which cytokine drives development of TH1 ?

Answer 7

Il-12

Question 8

What kind of immunity is TH2 involved in?

Why?

Answer 8

Humoral immunity against extracellular pathogens

Major effect is on B-lymphocyte, inducing class switch to IgE

Question 9

What does IgE do?

Answer 9

• Opsonises helminths and parasites

- stimulates mast cell degranulation

Question 10

Which antibody is present in hypersensitivity reactions?

Answer 10

IgE (mast cell degranulation to release histamine)

Question 11

What is cross presentation?

Answer 11

Ability of APC’s to present antigen/peptide on MHC 1 and MHC 2, thus activating naïve CD8+ and CD4+ T lymphocytes

Question 12

How do TH1 lymphocytes stimulate the differentiation of cytotoxic T cells?

Answer 12

• TH1 releases cytokines which causes differentiation of the CD8+ effector cell into CTL (cytotoxic lymphocyte)

Question 13

Naïve CD8+ cells are activated by?

What do they differentiate into?

Answer 13

Recognition of MHC

Effector CD8+ cells* /
Memory CD8+ cells

*(can become CTL)

Question 14

What makes up the variable region of the BCR?

Answer 14

distal ends of the heavy and light chains

Question 15

What limits the amount of antigens we can recognise and mount immune response against?

Answer 15

Our determined set of MHC molecules

bc the combinatorial diversity of TCR’s and BCR’s is very high

Question 16

Which 3 signals activate the B- cell?

Answer 16

1) BCR activation by antigen
2) T cell binding
(TCR/ MHC) and (CD28/ B7)
3) Cytokines and CD40 activation

Question 17

How does a T-cell bind a B-cell?

Answer 17

(B cell presents antigen in MHC 2 complex)

• TCR binds MHC
• CD28 on T cell binds B7 on B cell
• CD40 ligand on the T cell activates CD40 on B-cell.

Question 18

Which membrane protein is upregulated following BCR activation? (binding antigen)

Answer 18

B7 on the B cell

binds CD28 on T cell

Question 19

What does CD40 activation induce?

Which cell facilitates this binding?

Answer 19

Heavy chain class switching from IgM

T helper cell (has CD40 ligand)

Question 20

Which antibodies produced by B cells are thymus independent?

Answer 20

Only IgM

Other antibodies are generated by class switching stimulated by CD40 activation. T helper cells activate CD40

Question 21

What is affinity maturation of the B-cell antibody response?

What does IgM look like?

Answer 21

Repeated exposure to the antigen can enhance the antibody’s affinity for it

Star shaped pentamer of antibodies

Question 22

Benefits of the IgG response vs primary IgM?

Answer 22

Faster
Stronger
Lasts longer (antibodies stay in blood)
Higher affinity

Question 23

What is IgA useful for?

IgM role?

Answer 23

Mucosal immunity

Activates complement