B Cells And Antibodies

Question 1

Characteristic of the adaptive immune system

Answer 1

2nd line of defence
Variable recognition elements
Highly specific
Immunological memory (improves next response)

Question 2

What is an antigen

Answer 2

Molecular determinants that can be recognised by antibodies, B and T cell receptors and can induce immune responses

Question 3

What is an immunogenicity

Answer 3

Molecular determinants that induce or elicit an immune response e.g. antigens

Question 4

Name the B cell recognition molecules

Answer 4

Immunoglobulins (Ig)
Membrane-bound B cell receptors (BCR)
Soluble antibodies

Question 5

Describe the structure of antibodies

Answer 5

Glycoproteins consisting of 4 polypeptides, 2 identical light chains and 2 identical heavy chains.
Light chains can be lambda or kappa and only one is expressed on each B cell
4 disulphides bonds

Question 6

What are the 5 major antibody types depending on the H chain

Answer 6

IgA, IgD, IgE, IgG, IgM

Question 7

What is Fab and Fc

Answer 7

Antibodies are Y shaped, when cut into 3 pieces, the top pieces are called Fab and the bottom one is Fc

Question 8

Describe Fab

Answer 8

Vary in structure and ab proteins

Question 9

Describe Fc

Answer 9

No ab activity
Can bind to FC-binding receptors on
- phagocytic cells (—>opsonisation)
- NK cells and eosinophils (—>ADCC)
- Mast cells

Question 10

True or false: IgG is polymeric

Answer 10

False, IgA and IgM are polymeric, dimers and pentameters respectively
IgA can be both

Question 11

Characteristics of B cell receptors

Answer 11

Heavy chain transmembrane domain
Short cytoplasmic tail
Membrane form of antibodies

Question 12

What are the function of antibodies

Answer 12

Bindi to pathogens to inhibit them interacting wit targets
Opsonisation
Classical complement activation
Antibody dependant cell cytotoxicity (ADCC)
Degranulation

Question 13

How do antibidies activate ADVC

Answer 13

Antibody binds to antigens on target
NK cells receptors recognise antibodies
Activated NK cell (binder to receptor) starts (and signals) to kill the cell
Cell dies by apoptosis

Question 14

Describe process of degranulation by antibodies

Answer 14

IgE antibodies bound to pathogen or allergen interact with eosinophil FcR.
Worm bound antibodies binds with eosinophil bound FcR and releases granules with proteolytic enzymes

Question 15

Name defence against Helminths/parasites

Answer 15

IgE
Degranulation
Secretion of proteases and ROS

Question 16

Describe IgA

Answer 16

Multimer
Neutralising antibody secreted through epithelial cells
Protects mucosal surfaces; breast milk, saliva etc.
Resistant to proteases

Question 17

Describe IgD

Answer 17

Monomer

main BCR together with M on mature B cells where controls B cell activation

Question 18

Describe IgM

Answer 18

Multimer
1st antibody produces by plasma B cells in response to antigen
Good opsoniser
Potent activator of classical complement

Question 19

Describe IgG

Answer 19

Monomer
Most predominant in circulation
Activator of classical complement pathway
Good opsoniser
Placenta transfer - immunity to new borns
Neutralise pathogens

Question 20

Describe IgE

Answer 20

Degranulation of eosinophils —> defence against parasites

Degranulation of mast cells and basophils —> allergic reactions

Question 21

Define Antibody Repertoire

Answer 21

Total number of antibody specificities available to an individual