Lymphocyte receptors, B cells and antibodies Flashcards
for B cells and T cells, which part of their receptors are constant and which part is variable
tip is usually variable
variable region of antibody is made out of what parts
variable
diversity
joining
what is junctional diversity
junction between variable/diversity/joining segments is not precise-> nucleotides are added and removed from junctions during rearrangement
what happens when a b cell is activated
differentiation into plasma cell that produces antibodies
structure of antibody
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
what do variable and constant regions usually confer
variable regions determine specificity
constant regions determine class
classes of antibodies; how are subclasses named
A, D,E,G,M
igA1, igA2,3,4.. etc
antibody functions
neutralisation of toxins/viruses (block interaction with other cells)
opsonise
activate component cascade
particle agglutination
IgG characteristics/function and subclasses. how are the subclasses arranged
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)
igA forms, how does it move into the gut and what does it do there
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
igM characteristics
first antibody made in immune responses
pentameric
good for agglutination
igE characteristics
mast cells have igE fc receptor -> when allergens X-link with igE-> mast cell releases granules
people with allergies have lots of igE
what antibodies do b cells have on their surface
igM and igD
how does affinity maturation take place
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
where does class switching take place
in germinal centres in secondary lymphoid organs
what kind of cells are produced in germinal centres
b memory cells -> quiescent circulating cells-> affinity matured/class switched plasma cells-> go to bone marrow or intestine/long lived
primary vs secondary immune response
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
are normal b cell populations monoclonal or polycolonal? what about memory clones?
polyclonal
polyclonal too, due to somatic hypermutation in germinal centre
what is a chimeric antibody? example
mouse monoclonal engineered-> variable regions are associated with human constant regions; ends with -ximab
eg rituximab for B cell lymphoma
what is a humanised antibody? example
only variable region is from mouse;
ends with -zumab
omalizumab for servere asthma allergies
what are human monoclonal antibodies? example
fully human
-umab
adalimumab for inflammatory diseases
what happens in haemolytic disease of newborn;
solution
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
