4. B cells

Question 1

What is the difference between b cells and t cells?

Answer 1

B cells can recognise antigens in any biological form

Don’t need to communicate with another cell to be active

Question 2

What stage of B cell development does gene to make a pre-BCR rearrangement occur?

Answer 2

Pre-B cell

Question 3

What feature of development does the B cell go through while it is an immature B cell?

Answer 3

Gene rearrangement to replace surrogate light chains

Now has an Igm receptor

Question 4

What receptors are present on a mature B cell?

Answer 4

IgM and IgD

Question 5

What type of bond attaches the chains of an IgM receptor?

Answer 5

Disulphide

Question 6

Where are the genes for the heavy chain of the IgM located?

Answer 6

IgH locus on chromosome 14

Question 7

Which C region is essential to make an IgM BCR?

Answer 7

Cμ

Question 8

What allows variation within the V region of the IgM receptor?

Answer 8

Random recombination of VDJ segments

Question 9

What regions code for the light chain of IgM receptors?

Answer 9

Igκ on chromosome 2

or IgI on chromosome 22

Question 10

What is positive selection?

Answer 10

Expression of a complete BCR

Question 11

What is negative selection?

Answer 11

Discarded if bind to self-antigen too strongly

Question 12

Why are checkpoints not as stringent for B cells as T cells?

Answer 12

B cells have a much shorter lifespan

Question 13

Describe what happens when an antigen binds to the BCR

Answer 13

Triggers phagocytosis
Present antigen on MHC-II
Upregulation of CD40 (co-stim receptor) and cytokine receptors

Question 14

What happens between Antigen binding to a BCR and activation of the B cell?

Answer 14

B and T cells for the specific antigen meet in the lymph node

Question 15

How do helper T cells activate B cells?

Answer 15

Activated Th cells recognise antigen presented
T cell increases costimulatory molecules which bind to CD40 on B cells
Release cytokines to cause proliferation and differentiation of B cells

Question 16

What causes isotype switching?

Answer 16

CD40-CD40L interaction and cytokines released by the Th cells

Question 17

What is affinity maturation?

Answer 17

Affinity of antibodies produced in response to an antigen increase with prolonged or repeat exposure

Question 18

What is an epitope?

Answer 18

Any biological molecule

Question 19

What is the first antibody made by B cells?

Answer 19

IgM

Question 20

What are the functions of Ig?

Answer 20

Activate complement

Clump microbes for elimination

Question 21

What is the most common antibody?

Answer 21

IgG

Question 22

What are the functions of IgG?

Answer 22

Neutralisation
Agglutination
Opsonisation
Complement activation

Question 23

What antibody can cross the placenta?

Answer 23

IgG

Has implications in grave’s disease

Question 24

What are the roles of IgE?

Answer 24

Fight helminth disease and cause allergic reactions

Question 25

What receptors does IgE bind to on eosinophils?

Answer 25

FcεR

Question 26

What receptors does IgE bind to during an allergic reaction?

Answer 26

Fc receptors on basophils and mast cells

Question 27

What role does IgA play in immunity?

Answer 27

Mucosal immunity

Question 28

Where is IgA produced?

Answer 28

Mucosal lymphoid tissues

Question 29

How is IgA transported across epithelia?

Answer 29

poly-Ig receptors

Question 30

Which antibody is acquired through breastmilk?

Answer 30

IgA

Question 31

What vaccine stimulates IgA immunity?

Answer 31

Oral poliovirus vaccine

Question 32

What is the least common antibody?

Answer 32

IgD

Question 33

What is the role of IgD?

Answer 33

Bind to mast cells and basophils to cause the production of anti-microbial peptides

Question 34

What are the regions on an antibody?

Answer 34

Antigen binding site Complement binding site Fc portion

Question 35

What are the functions of antibodies?

Answer 35

``` Neutralisation Opsonisation and phagocytosis Complement activation Antibody-dependent cellular toxicity Eosinophil/mast-cell mediated reactions ```

Question 36

What is neutralisation?

Answer 36

Antibody binds to microbes and toxins and stops them from entering cells

Question 37

What receptor is IgG recognised by?

Answer 37

FcyR1 on neutrophils, macrophages and DCs | Which increases phagocytosis

Question 38

What binds to the complement binding site on an antibody?

Answer 38

C1q

Question 39

What is antibody related cellular toxicity?

Answer 39

NKs bind to antibody coated cells and destroy them

Question 40

What receptor on NK cells binds to IgG?

Answer 40

FcyRIII

Question 41

What is CVID?

Answer 41

Common Variable Immune Deficiency | Lack IgG, M and A

Question 42

What does CVID result in?

Answer 42

Infections of lungs and GIT from age 6

Question 43

How is CVID treated?

Answer 43

IV Ig

Question 44

What is selective IgA deficiency?

Answer 44

B cells fail to differentiate into IgA producing plasma cells Have recurrent sinopulmonary infections

Question 45

What disease is selective IgA deficiency associated with?

Answer 45

Coeliac's disease

Question 46

What is x-linked Agammaglobulinaemia?

Answer 46

Mutation in Bruton's tyrosine kinase B cells are absent Recurrent bacterial infections starting from 3-6 months