B cells and Antibodies Flashcards
What are the 2 types of antigen epitope
linear and conformational
what are conformational epitopes
epitopes formed by amino acid residues not in linear sequence but spatially juxtaposed
what are the secondary antibodies
IgG IgA IgE
what is effective immunity
may get infected and transmit virus but no symptoms
what is sterilising immunity
will not get infected or transmit virus
how is antibody diversity generated
clonal selection memory b cells subclass switching somatic mutations allelic exclusion
what is the clonal selection theory
antigens select appropriate antibody from existing pool
how many potential antigen binding sites does IgM have
10
5 effective
what is the first antibody made in response to infection
IgM
what is IgM involved in
complement activation and bacteria/virus neutralisation
what antibody can cross the placenta
IgG EXCEPT IgG2
what type of IgA is mainly found in secretions
IgA2
what is IgE involved in
worm infections and hypersensitivity
how many aas are in the light chain of antibodies
212
how many aas are in the heavy chain of antibodies
240
what are the 6 mechanisms for the generation of antibody diversity
- germ line V genes
- V-J V-J-D recombination
- n nucleotide addition
- recombinational inaccuracies
- somatic hypermutation
- assorted heavy and light chains
how does VJD junctional diversity occur
nucleotides are randomly deleted and inserted
- interrupts codons
what is allelic exclusion
co expression of both maternal and paternal alleles are prevented
when does antibody class switching occur?
around 28 days
what region of the antibody changes in class switching
Fc
what cytokines play a role in class switching
IL4 - IgG4 and IgE
IFNy - IgG2
what is the mode of action of antibodies
direct neutralization
opsonisation of pathogen promotes ADCC
activation of complement - lysis
what does ADCC stand for?
antibody dependent cellular cytotoxicity
what is ADCC
antibody opsonized virus infection cells and cancer cells killed by CTL and NK cells
what are the antibody producing B cells
plasmablasts, SLPCS, LLPCS, memory b cells
what are plasmablasts
secrete low affinity antibodies - short lived, early
what are SLPCs
short lived plasma cells that produce large amounts of both IgG and IgM antibody, survive for 2 weeks
what are LLPCs
long lived plasma cells that enter a GC and produce antibody for months-years
what are memory b cells
GC derived, class switched and hypermutated -lifelong immunity
what is damaged/lost in severe COVID19
germinal centers
bcl6+ b cells and bcl6+ Tfh cells
what brings about affinity maturation of antibody
somatic point mutations in V gene
examples of subunit vaccines
covid novavax
hep b
HPV
what are the mRNA vaccines for covid
moderna and pfizer
what are the virus vector vaccines for covid
astrazeneca
what is the HAMA effect against mabs
develops antibodies against mab
what therapies are mabs used for
rheumatoid arthritis - against inflammatory cytokines
