Lymphocyte receptors, B cells and antibodies

Question 1

for B cells and T cells, which part of their receptors are constant and which part is variable

Answer 1

tip is usually variable

Question 2

variable region of antibody is made out of what parts

Answer 2

variable
diversity
joining

Question 3

what is junctional diversity

Answer 3

junction between variable/diversity/joining segments is not precise-> nucleotides are added and removed from junctions during rearrangement

Question 4

what happens when a b cell is activated

Answer 4

differentiation into plasma cell that produces antibodies

Question 5

structure of antibody

Answer 5

2 heavy chains inside (joined by disulfide bonds)
2 light chains on the outside (also joined by disulfide bonds)
variable regions at the top only

Question 6

what do variable and constant regions usually confer

Answer 6

variable regions determine specificity

constant regions determine class

Question 7

classes of antibodies; how are subclasses named

Answer 7

A, D,E,G,M

igA1, igA2,3,4.. etc

Question 8

antibody functions

Answer 8

neutralisation of toxins/viruses (block interaction with other cells)
opsonise
activate component cascade
particle agglutination

Question 9

IgG characteristics/function and subclasses. how are the subclasses arranged

Answer 9

main serum antibody
specific igG measured in response to vaccine
opsonisation
agglutination to pathogens-> target for NK (antibody dependent cellular toxicity)
IgG1,2,3,4 (in decreasing order of abundance)

Question 10

igA forms, how does it move into the gut and what does it do there

Answer 10

igA is a monomer in serum
dimer on mucosal surface, dimer is formed by J chain
igA has secretory component (Carbohydrate-rich)-> attaches to basolateral surface of epithelial gut cell-> transport into gut lumen -> agglutinates bacteria -> retains antigen by attaching to mucosal surface of gut

Question 11

igM characteristics

Answer 11

first antibody made in immune responses
pentameric
good for agglutination

Question 12

igE characteristics

Answer 12

mast cells have igE fc receptor -> when allergens X-link with igE-> mast cell releases granules
people with allergies have lots of igE

Question 13

what antibodies do b cells have on their surface

Answer 13

igM and igD

Question 14

how does affinity maturation take place

Answer 14

germinal centres contain dividing B cells-> if B cells encounter specific antigen + help from Th2 cells-> rapid division-> somatic hypermutation (mutate ig variable region)-> high affinity variants selected-> affinity maturation

Question 15

where does class switching take place

Answer 15

in germinal centres in secondary lymphoid organs

Question 16

what kind of cells are produced in germinal centres

Answer 16

b memory cells -> quiescent circulating cells-> affinity matured/class switched 
plasma cells-> go to bone marrow or intestine/long lived

Question 17

primary vs secondary immune response

Answer 17

primary: igM rises first-> class switch to igG which peaks after 15 days 
secondary-> igM rises first-> class switch to igG which peaks to a greater level by 15 days

Question 18

are normal b cell populations monoclonal or polycolonal? what about memory clones?

Answer 18

polyclonal

polyclonal too, due to somatic hypermutation in germinal centre

Question 19

what is a chimeric antibody? example

Answer 19

mouse monoclonal engineered-> variable regions are associated with human constant regions; ends with -ximab
eg rituximab for B cell lymphoma

Question 20

what is a humanised antibody? example

Answer 20

only variable region is from mouse;
ends with -zumab
omalizumab for servere asthma allergies

Question 21

what are human monoclonal antibodies? example

Answer 21

fully human
-umab
adalimumab for inflammatory diseases

Question 22

what happens in haemolytic disease of newborn;

solution

Answer 22

mother who is rh- has igG against rh+ following exposure to rh in first pregnancy-> in second pregnancy, cross placental transfer of antibodies to fetus-> RBC lysis
plasmapheresis: igG removed from baby’s blood