Effector function and humeral immunity

Question 1

What is the difference between T cell dependent and T cell independent activation of B cells?

Answer 1

• T cell dependent, T helper cell is required for activation
• T cell independent only need engagement of receptors and complete receptors of B-cell

Question 2

What are the functions of B cells activated by the T cell dependent pathway? [4]

Answer 2

• istotype switching
• high affinity antibodies
• memory b cells
• long lived plasma cells

Question 3

What are the functions of B cell activated by T cell independent pathways?

Answer 3

• production of mainly IgM
• low affinity antibodies
• short lived plasma cells

Question 4

What is the difference between the dark and light zone in the geminal centre? [2]

Answer 4

• Dark zone there is lots of proliferation and isotope switching
• light zone B cells with strong binding receptor release plasma and effector cells

Question 5

What is meant by hypermutation [2]

Answer 5

• editing of variable regions
• in the geminal centre (dark zone)

Question 6

What is the purpose of hyper mutations [2]

Answer 6

• better binding of antigens to pathogens
• stronger immune response

Question 7

What is meany by isotope switch [2]

Answer 7

• fc region of antibody changed in heavy region
• retains the same variable regions

Question 8

What is the purpose of isotope switching?

Answer 8

• alter the immune response
• antigens can be specialised for certain parts of the body

Question 9

What is the role of AID?

Answer 9

• enzyme that breaks and cuts out parts if intersecting DNA
• to change the variable regions during hypermutation

Question 10

Why do IgA antibodies shave the highest production? [3]

Answer 10

• They can cross the epithelium layer easily
• found in GI and respiratory tracts
• where most pathogens are encountered

Question 11

Which antibodies are involved in passive immunity? [2]

Answer 11

IgG1 and IgG3

Question 12

Which antibodies are produced first in an immune response [2]

Answer 12

IgM and IgG3

Question 13

Which antibodies are monomers [3]

Answer 13

IgD IgG IgE

Question 14

Which antibody can be both a monomer and a dimer? [1]

Answer 14

IgA

Question 15

What determines the isotype of an antibody? [1]

Answer 15

cytokines produced by T cells
CD40

Question 16

Describe how the switch region is altered [5]

Answer 16

• cytokines activate specific promoters
• RNA polymerase reads switch regions when instated by upstream promoters
• AID and other enzymes introduce clustered nicks on both strands of DNA
  -repair proteins initiate double stranded break repair
• DSBR machinery joins two switch regions

Question 17

Identify some functions of the humoral response [6t]

Answer 17

• neutralisation of microbes and toxins
• opsonisation and phagocytosis pf microbes
• antibody dependent cellular cytotoxicity
• inflammation
• lysis of microbes
• complement actuation

Question 18

Describe how antibodies cause neutralisation [5]

Answer 18

• bind to pathogen
• preventing its ability to cross epithelial barrier
• blocks the pathogen binding to and infecting cells
• binds to toxin
• so toxin can’t bind to cellular receptor

Question 19

Describe the process of opsonisation [4]

Answer 19

• IgG opsonises microbe
• opsonised microbe binds to phagocyte Fc receptors
• activating phagocyte
• phagocytosis of microbe

Question 20

What is the roll of mast cells [3]

Answer 20

• large cells found in connective tissue
• have granules containing histamines and inflammation mediators
• leads to inflammation when activated

Question 21

Describe how IgE antibody cross linking leads to mast cell activation [4]

Answer 21

• mast cells coated in IgE antibodies
• mast cells gain specificity by binding to innate immune cells
• multivalent antigen cross links between IgG antibodies
  -leads to release of granule contents