Immunology Part 4

Question 1

How long does the adaptive immune system take to respond?

Answer 1

Days-weeks

Question 2

What method of recognition does the adaptive immune system use to recognise pathogens?

Answer 2

Antigens: antigen receptors

Question 3

What are antigens?

Answer 3

any substance which can stimulate the adaptive immune system

Question 4

What do CD4T+T cells do?

Answer 4

key regulators of the entire immune system

Question 5

What do CD8+T cells do?

Answer 5

Kill virally infected body cells

Question 6

How many antigen receptors do T and B cells express?

Answer 6

Multiple copies of one receptor

Question 7

How do T cells recognise an antigen?

Answer 7

T cell antigen receptor (TCR)

Membrane-bound αβ heterodimer

Question 8

How do B cells recognise antigens?

Answer 8

B cell antigen receptor (BCR)
Membrane bound antibody (IgM or IgD)
Light chain and heavy vhain

Question 9

What are antibodies also known as?

Answer 9

Immunoglobulins

Question 10

Where are antibodies produced?

Answer 10

By B cells in response to antigen

Question 11

What do B cells do with antibodies?

Answer 11

Express them on their surface

Secreted as soluble proteins in extracellular fluids

Question 12

What holds the two Ig light and Ig heavy chains together?

Answer 12

Disulphide bonds

Question 13

What does each Ig heavy and Ig light chain contain?

Answer 13

Variable region and a constant domain

Question 14

What are the heavy chains found in the following?

	    IgM 
	    IgG
	    IgA 
	    IgE 	    
            IgD

Answer 14

micro
gamma
alpha
epsilon
sigma

Question 15

What forms the antigen binding site?

Answer 15

Hypervariable regions of Ig light and Ig heavy chains combined

Question 16

How can the body defend against millions of antigens?

Answer 16

Process of gene rearrangement is entirely random
Gives rise to hugely diverse B cell and T cell populations
Potential for generation of auto-reactive cells

Question 17

Where do adaptive immune responses occur?

Answer 17

Secondary lymphoid tissues

Question 18

How do antigens enter a lymph node?

Answer 18

1. Particles and antigens derived from pathogens are released by phagocytes
2. Inflammatory cytokines stimulate immature, tissue-resident dendritic cells –> expression of co-stimulatory molecules
3. dendritic cells recognise and phagocytose pathogen-derived particles and antigens
4. Dendritic cells dies the internalised pathogen-derived antigens and display small peptides on surface in complex with MHC proteins
5. Pathogen derived particles, antigens and mature dendritic cells travel to local draining lymph nodes

Question 19

What do MHC proteins do?

Answer 19

display peptide antigens to T cells

Question 20

What are the two classes of MHC proteins?

Answer 20

Class I MHC

Class II MHC

Question 21

Describe MHC I

Answer 21

Expressed on all nucleated cells

Present peptide antigens to CD8+T cells

Question 22

Describe MHC II

Answer 22

Expressed only on professional antigen presenting cells

• dendritic cells
• macrophages, B cells

Present peptide antigen to CD4+T cells

Question 23

What two signals does T cell activation require?

Answer 23

MHC binding to TCR

B7 binding to CD28

Question 24

What is the role of stromal cells?

Answer 24

Trap opsonised antigens in B cell zones

Question 25

What two signals does B cell activation require?

Answer 25

Protein antigen;
Signal 1:BCR + antigen
Signal 2: TFH cell help

Any antigen;
Signal 1: BCR + antigen
Signal 2: PRR + PAMP

Antigens with repetitive antigenic epitopes;
Signal 1 + 2 : multiple BCRs engaged

Question 26

What can B cells do that T cells cannot?

Answer 26

Can recognise antigens independent of MHC molecules

Question 27

Describe the fate of antigen activated B cells and T cells

Answer 27

Resting cells
-specific antigen + co-stimulation

Activated cells
-Entry into cell cycle, mitosis

Clonal expansion
-differentiation

Effector cells and T cells