Adaptive Immunity

Question 1

Difference between T cells and B cells

Answer 1

T cell receptors are heterodimers: made up of a beta and alpha subchain and can bind one antigen. T cells made in thymus.

B cells have two binding sites for antigens, and are made up of 4 chains, 2 identical light and 2 identical heavy. B cells made in bone marrow.

Question 2

Composition of the variable part of antigen receptors heavy chain and light chain

Answer 2

Heavy chain: Variable, Diversity, Joining

Light chain: Variable, diversity, joining

Question 3

Combinatorial diversity

Answer 3

combination of segments from light and heavy chains to generate unique receptors from multiple alternative segments.

Question 4

Junctional diversity

Answer 4

When nucleotides are removed or added from junctions between segments during rearrangement.

Question 5

Function of antibody IgG

Answer 5

Opsonisation, antibody-dependent cellular cytotoxicity

Question 6

Function of antibody IgA

Answer 6

Defensive mucosal defense in the gut. Produced on basolateral side, then is transported into lumen by secretory component. In lumen, (1) agglutination and (2) retention of antigen in mucus by binding to mucus with CHO rich SC.

Question 7

Function of antibody pentametric IgM

Answer 7

First antibodies responding. Agglutination -> pentametric means 5 IgMs are connected together, so they have 10 binding sites bind very well.

Question 8

Function of antibody IgE

Answer 8

Binds to mast cells when no allergens present. When allergen present, it binds to IgE and causes degranulation of mast cell (release of histamine and others).

Question 9

Somatic hypermutation

Answer 9

When antibodies enter germinal centers and reproduce and mutate profusely. This gives rise to many slightly different antibodies.

Question 10

Selection in germinal centers

Answer 10

Antibodies produced from somatic hypermutation are tested against antigens and only the ones which binds the best are kept.

Question 11

Affinity Maturation

Answer 11

somatic hypermutation + selection of antigens with most affinity.

Question 12

2 types of cell that leave germinal center

Answer 12

Memory B cells: better afinity for antigen and maybe class switched. 
Plasma cells: go to bone marrow or intestines and produce protective antibodies for a lifetime.

Question 13

Monoclonal antibodies

Answer 13

Antibodies made by identical immune cells which can be used therapeutically.

Question 14

Chimeric monoclonal antibody definition and ending

Answer 14

Mouse variable region is attached to human constant region. Ending ximab.

Question 15

Humanised monoclonal antibody definition and ending

Answer 15

Only part o the variable region contacting antigen is mouse. Ending zumab.

Question 16

Human monoclonal antibody definition and ending

Answer 16

Fully human antibody. Ending umab.

Question 17

An AB blood would have antibodies for?

Answer 17

Nothing.

Question 18

An O blood would have antibodies for?

Answer 18

A and B antigens.

Question 19

What is rhesus antibody. And possible danger on fetus.

Answer 19

Antibody on RBC. Someone can be Rh - so they have the rhesus antibody. Dangerous is mother has it but baby doesn’t because it destroys baby RBC. Treated with plasmapheresis.

Question 20

MHC I molecule structure and location

Answer 20

Single chain receptor with peptide binding groove. Expressed on all nucleated cells

Question 21

MHC II molecule structure and function

Answer 21

Double chain (alpha and beta) with peptide binding groove, expressed on antigen specialized presenting cells.

Question 22

Locus of genes encoding MHC class I and II

Answer 22

Short arm of chromosome 6

Question 23

Structure of T-cell receptors

Answer 23

Heterodimer (2 different chains joined by disulphide bond). Variable constant domains.

Question 24

Effect of activated CD8 T cell

Answer 24

kills cells presenting peptide by cytotoxicity, cell to cell interactions, citokines.

Question 25

Effect of activated CD4 T Cells

Answer 25

Differentiated into Th1, Th2, Th17 and TREG

Question 26

Effect of Th1 (produced by CD4)

Answer 26

1. Proliferation of cytotoxic cells (IL2)

2. Enhance killing capabilities of macrophages (IFNy)

Question 27

Effect of Th2 (produced by CD4)

Answer 27

Promotes proliferation of B cells (IL4, IL13)

Question 28

Effect of Th3 (produced by CD4)

Answer 28

Mucosal support and attract cells to the site of infection (IL17, IL21, IL22)

Question 29

Immune Tolerance

Answer 29

Ability to not elicit a response on a self-tissue that you could be doing.

Question 30

Mechanisms of Immune Tolerance (central and peripheral)

Answer 30

Thymic Education
Peripheral mechanisms:
1. Anergy
2. Regulatory T-cells

Question 31

3 steps of Thymic Education and location.

Answer 31

1. Expression of a functional TCR (TCR produced and non-functional die).
2. Positive selection of self MHC (Cells with an affinity for MHC I and II selected and CD component selected). Thymic cortex.
3. Negative selection to eliminate high-affinity self-reactive T cells. Thymic medullary epithelial cells.

Question 32

Anergy

Answer 32

T cell that has encountered antigen with no co stimulation will remain in the circulation but will be unresponsive to future stimulation.

Question 33

What anergy is important for

Answer 33

1. Human antigens not expressed in thymus
2. Food antigens
3. Good bacteria antigen

Question 34

Regulatory T Cells functions

Answer 34

inhibit proliferation of effector t-cells
Reduce their cytokine production
Reduce co-stimulation

Question 35

Regulatory T Cells 2 main subtypes

Answer 35

aTreg: adaptive, developes in periphery, food antigens.
nTreg: naturally occuring produced in thymus protects against autoimmunity.

Question 36

IPEX

Answer 36

Multiple autoimmune diseases