B cells: memory and immunization Flashcards
Describe primary response - memory
Most igm producing cells (some igd) - come from primary focus
Some B cells will go to germinal center = undergo somatic hypermutation and class switching late in response
Describe secondaru response - memory
Some memory B cells make igm
Most memory B cells express igg (some iga and ige) - and will undergo further somatic hypermutation = increase affinity and secrete more abs
What does repeated immunization lead to
Increasing affinity of abs due to somatic hypermutation and affinity maturation—> can re enter germinal center
What do memory B cells express
Express class switched surface ig isotype - igg bearing B cells tm
Express higher levels of mhc class 2, cd40 and receptors for survival and proliferation than B cells =binding more quick and effective
Memory B cells expression of higher levels of mhc class 2, cd40 and receptors =helps
Helps memory B cells acquire and present antigens more efficiently to tfh than naive B cells
Increases ab production
Where are memory B cells
Circulate through blood and take up residence in spleen and ln (secondary lymphoid organ)
Describe memory T cells
At least 90% of effector T cells die by apoptosis after pathogen cleared
Leaving behind ag specific memory T cells
Describe what surface markers can be used for
Surface markers used to broadly distinguish naive, effector and various memory T cell subsets in mice
Describe phenotype of memory T cells
Phenotypically unique = closer to effector T cells than naive T cells
What do memory T cells need
Less requirements for activation
No need for strong costimulatory signals or cytokines - memory T cells have large expression cd28-signal 2
Still require contact with Pmhc but more sensitive to stimulation and respond much faster
What happens when memory T cells reactivated
Become effector
Tcm cells = where
Reside in/travel between secondary lymphoid tissues (leaves thymus)
Tcm cells = fucntion
Rapidly reactivated by second ag exposure
Can differentiate into several subset types deepening on cytokine environment- any type T cell
Tem cells = where
Travel to/between tertiary tissues. Like skin
Tem cells fucntions
Contribute to better first lien defences = interact with local apcs
Shift right back into effector fucntions on second ag exposure- cycling
Trm cells = where
Permanent residents of previously infected tissues
Trm cells = function
Respond upon reinfection
Cd8+ Trm found in multiple tissues (cd4+ Trm hard to find since moves around)
Describe memory T cells fate determinants = what are they
Cytokines = il17, il15
Notch1
Strength of ag interaction = lead T cells to be memory
Describe memory T cells fate determinants = il17
Il17 pro survival cytokine = can lead to increased expression bcr-2 (anti apoptotic = stays alive)
Expression of il17ralpha (indicator of resident memory t cell) = downregulated during effector T cell differentiation but retained or reacquired by those cells destined to become memory T cells
Compare memory cd8+ and cd4+ T cells
CD8 MEMORy T cells =more abundant than memory cd4+ T cells
Memory cd8+ t cels still need help of cd4+ T cells for longevity (activation, licensing )
Define immunize
Make someone resistant to particular infectious disease or pathogen
Protective immunity
Achieved by active or passive immunization
Passive immunity
Temporary immunity conferred by transfer of immune products, like abs (antiserum), from immune individual to non immune one
Like mabs or breastmilk
Active immunity
Adaptive immunity induced by natural response to pathogen or by vaccination = immune system activated v
