lecture 2- adaptive immunity Flashcards
define dendritic cell maturation
professional APC’s, can travel from sites of infection to draining lymph nodes and inform B and T cells of what is going on
- go from resting to mature DC’s after exposure to PAMP’s or inflammatory stimuli
dendritic cells communicate between the ___ and ___ systems
innate and adaptive
location of immature vs mature DC’s
immature: tissue resident
mature: lymph nodes
uptake capacity of of immature vs. mature DC’s
immature: highly endocytic and phagocytic
mature: endocytosis shuts down
costimulatory molecule expression of immature vs. mature DC’s
immature: low level
mature: high level
MHC expression level in immature vs. mature DC’s
immature: low level
mature: high level
T cell stimulatory activity in immature vs. mature DC’s
immature: poor stimulators
mature: high stimulators
describe infection to immunity process
DC’s pick up, process, and present bacteria into peptides on cell surface- migrate to draining lymph nodes to interact with T cells- clonal expansion, move back to site of infection to kill and clear
describe lymph node structure
T and B cells are partitioned into their own zones
- the 2 zones are very close to each other- have communication
- B cell zones called follicles or germinal center
primary lymphoid organs are sites at which leukocytes undergo ___ (___) and ___
hematopoiesus (development and differentiation)
selection
name primary lymphoid organs
bone marrow & thymus
Secondary lymphoid organs are most often the site of T cell and B cell ___
activation
describe the receptors of adaptive immunity
- B cell receptor can be expressed on cell surface or secreted (antibody)
. has 2 identical heavy chains & 2 identical light chains
. antigen binding site formed by 1 heavy chain variable region and 1 light chain variable region - T cell receptor always on cell surface (transmembrane)
- B cell has 2 antigen-binding sites, T cell receptor has 1
name the 4 life stages of B and T cell
- formation of a receptor
- selection
- activation
- differentiation
describe the life stage of formation of a receptor
Must form a unique highly specific receptor, rearrangement events
describe the life stage of selection
-To not recognize self (avoid auto-recognition)
-Selects for T cells, T cells need antigen to be processed and presented by MHC
describe life stage of activation
travel out of primary organs to lymph nodes where they constantly search for the signals to activate them
describe life stage of differentiation
- B cells can make their antigen presenters better, numerous rounds of proliferation- higher affinity stay, lower don’t
- Memory: proliferation, then contraction and apoptosis of most effectors, a few remain and stay in memory
Prior to rearrangement, B cell receptor and TCR genes are said to be in _____. After rearrangement, the DNA of B and T cells is ____
germline configuration
permanently changed
gene rearrangment is often referred to as ______, why?
somatic recombination
only happens in somatic cells, not germ cells (sperm and egg)
describe T cell diversity- clonal expansion
each T cell has a unique specificity for antigen
- starting “repertoire” of T cells — cell “presenting” antigen for T cells — clonal expansion — effector cells contracted, memory cells stay
B cells see _____
T cells see _____
B cells see native antigen through BCR
T cells see antigenic peptides (digested or processed pieces of antigens) presented by MHC molecules
what does it take for a T cell to recognize antigens?
antigen processing and presentation
- DC takes up pathogen for degradation, pathogen taken apart inside DC
- pathogen proteins are unfolded and cut into small pieces
- peptides bind to MHC molecules and complexes go to cell surface
- T-cell receptors bind to peptide; MHC complexes on DC surface
