EXAM 4-2

Question 1

Does genetic makeup have an effect on the immune response of a person?

Answer 1

YEs

Question 2

What are ‘holes in the repetoire’?

Answer 2

Immunodeficiency because of a poor Ig or TCR variable region due to the absence of a gene

Question 3

Which three mechanisms account for class-2-linked high and low responsiveness?

Answer 3

Antigen presentation: processing of the antigen might not give a well-fitting peptide

T-cell repertoire : lack of T-cells specific for the foreign antigen due to hole in repertoire

T-cell mediated suppression: regulatory cell activity which suppresses response to complex antigens

Question 4

Name three factors that influence the immunodominance of a certain antigen

Answer 4

• relative affinity of the BCR for their respective epitopes
• Frequency of T- and B-cells with antigen receprtos for different epitopes of the antigen
• ability to generate antigenic peptides that have strong affinity for the MHC groove

Question 5

How does recognition of C3d lead to enhanced B-cell activation?

Answer 5

Recognition of C3d-coated antigens leads too crosslinking of the BCR and the CD21 complesx receptor with CD19. This enhances the B-cell activation through stimulatory signalling pathways

Question 6

How can the antibody response be inhibited?

Answer 6

Crosslinking of the BCR to FCyR2b with ITIM leads to tyrosine phosphorylation of CD19, leading to inhibition of the antibody complex

Question 7

What is epitope masking?

Answer 7

Prevention of access to epitopes on the antigen by antibody, preventing B-cell responses

Question 8

What is activation-induced cell death (AICD?)

Answer 8

It limits excessive proliferation of the antigen and therefore the immune response.
T-cells upregulate death receptors and if ligands are on cell surface, they get apopotosed.

Question 9

What is the role of FLIP in death receptor-mediated AICD?

Answer 9

FLIP determines the fate of a cell, when the death receptor is engaged by the ligand. It inhibits recruitment of caspase into death induced signal complexes

Question 10

Name three negative immune system regulators and what they lead to

Answer 10

PD1-PDL1/PDL2
CTLA4-CD80/Cd86
BTLA-HVEM
They lead to reduced cytokine production, reduced proliferation and differentiation, and decline in cell survival

Question 11

Which three subpopulations are considered helper T-cells?

Answer 11

IFNy-secreting Th1 cells
IL-4-secreting Th2 cells
IL-17 secreting Th17 cells

Question 12

What is T-cell mediated suppression?

Answer 12

Unresponsiveness induces by a high dose of antigen leading to suppressing of specific antibodies on T-cells

Question 13

Which two types of T-regs are there? What do they express?

Answer 13

Naturally occuring Tregs (nTregs) that express Foxp3 as soon as they are produced in the thymus
Inducible Tregs (iTregs) which arise in the periphery and express Foxp3 and CD25 upon activation

Question 14

What do MDSCS, myeloid-derived suppressor cells, do?

Answer 14

They limit T-cell responses through many mechanisms. One is the depletion of L-arginine, which arrests cell proliferation

Question 15

How do hormones impact immune responses?

Answer 15

Immune cells receive signals from hormones. Glucocorticoids and androgens depress response while estrogens, GH, thryoxine and insulin increase response

Question 16

How does diet related to immune respnse?

Answer 16

protein-calorie malnutrition leads to impaired immune responses.
So do some vitamin deficincies, like B6, B9,C, and E.
Vitamin A and D also change the immune response by modulating it. They inhibit Th17 cells, promote Th2 cells

Question 17

Is there a difference in gender in the immune system?

Answer 17

Yes, females have stronger immune response and are more susceptibile to auto-immune disease

Question 18

Does age impact response of the immune system?

Answer 18

Yes, elderly are more susceptible to infection. Both adaptive and innate immune system decline with age.

Question 19

By which two major stimuli are immune responses instigated?

Answer 19

By PAMPS and DAMPS

Question 20

What is the signifance of the PAMP for the immune response?

Answer 20

The PAMP signature tells the type of infection that the innate immune cells are dealing with, leading to the correct t-and b-cell effector responses

Question 21

Name three effector mechanisms of the innate immune system

Answer 21

• opsonization of pathogens through soluble PRRs
• direct phagocytosis of pathogens via cell-associated PRRs
• Direct lysis of pathogens via soluble PRRs

Answer 22

Cells of the innate immune system give permission to the adaptive immune system to respond to antigen

Question 23

Name five effector functions of the adaptive immune system

Answer 23

antibody-mediated opsonization of pathogens causing phagocytosis
antibody-mediated opsonization of pathogens causing complement activation
Enhancement of NK cells to kill through ADCC
T-cell mediated killing of virally infected or transformed cells
Production of cytokines by T-cells