Flashcards in Immunological Memory Deck (47)
What are the differences between the primary and secondary responses of B cells?
higher frequency of antigen specific B cells; produce IgG or IgA rather than IgM; higher affinity and higher level of somatic hypermutation
How can memory B cells be created?
either from the primary response germinal center reaction or independently of hte germinal centre reaction from short-lived plasma cells
Where do memory B cells take up residence?
spleen and lymph nodes
What markers distinguish memory B cells from naive B cells and plasma cells?
switched surface Ig isotype (rather than just IgM or IgD- whilst plasma cells have very low surface Ig; CD27 is found on memory B cells and naive T cells ; memory B cells have higher levels of MHC II and B7.1
what does Cd27 on memory B cells and naive T cells bind to?
CD70 expressed on dendritic cells
What is the difference between isotypes of antibody produced in the primary response vs the secondary response?
secondary response produces relatively little IgM; lots of IgG and some IgA and IGE
Why do memory cells have higher levels of MHC II and B7.1?
memory B cells can acquire and present antigen more efficiently to Tfh cells so they can help stimulate the antibody repsonse
What causes the affinity of the antibodies produced during secondary and tertiary responses to rise progressively?
memory B cells can reenter germinal centers and undergo additional somatic hypermutation and affinity maturation
What protein do memory T cells express more of than activated T cells?
Bcl-2 : promotes cell survivial
What markers do activated T cells express that memory T cells don't ?
What important markers differentiate memory T cells from effector T cells?
alpha subunit of hte IL7 recceptor (expressed by naive T cells but not effector)
What do naive T cells require to survive?
require contact with self peptide:selfMHC complexes as well as IL7
What cytokines does the survival of memory T cells rely on?
IL7 and IL15 (CD8)
What is the homing receptor taht directs T cells into secondary lymphoid tissues?
What homing receptor is found on effector and memory T cells instead of L-selectin?
CD44- expressed in peripheral tissues
Why do memory T cells express CD44 instead of L-selectin?
means they can migrate from the blood into peripheral tissues rather than migrating directly into lymphoid tissues
What is CD45?
a surface protein tyrosine phosphatase expressed on all haematopoietic cells
What cells is the CD45RO isoform found on?
effector and memory T cells
What chemokine receptor do central memory T cells express?
What is the function of central memory T cells?
recirculate similarly to naive T cells, traffic throug the T zones of peripheral lymphoid tissues
What is the pattern of migration of naive T cells?
migrate from the blood, into the secondary lymphoid organ then into the lymphatics and back into the blood
What is the differnece between central memory T cells and otehr memory T cells?
very sensitive to cross-linking of their T cell receptor and rapidly express CD40L in response but become effectors relatively slowly
What markers do effector memory T cells possess?
lack CCR7 but express b1 and b2 integrins
What is the function of effector memory T cells?
rapidly enter inflamed tissues and rapidly mature into effector T cells
What cytokines do effector T cells produce soon after stimulation?
IFNy; IL-4 and IL-5
What is hte migration pattern of effector T cells?
migrate from blood into peripherl non-lymphoid tissues then into lymphatics--secondary lymphoid tissues--lymphatics--blood
What is different about tissue resident memory T cells compared with central and effector memeory T cells?
do not migrate but take up residence in epithelial sites
What does TGF-b production by epithelial cells cause in the Trm?
Trm cells express ae:b7 which binds E-cadherin expressed by the epithelium and is required for Trm retenion
What happens when Tcm cells are stimulated by antigen?
lose expression of CCR7 and differentiate into Tem cells