EXAM 3 T Cell-Mediated Immunity Flashcards
Describe CD8 T cells
- kills infected or diseased cells
- direct effector T cell arm
- targeted
- repeated activity until inhibited
describe CD4 T cells
- enhance innate and adaptive immunity
- regulatory T cell arm
- targeted
- direct and indirect effector functions; can kill
describe the basic process of T cell activation and differentiation
for both CD8 and CD4 T cells:
- antigen presenting cell interacts with naive T cell (antigen recognition)
- T cells are activated by IL-2 and IL-2R (same for CD8 and CD4)
- clonal expansion
- differentiation
- effector cell and memory cell
- CD4 - activation of macrophages, B cells, other cells
- CD8 - killing of infected target cells; macrophage activation
___ initiates T cell immunity
antigen presentation
___ are the most common T cell activator
dendritic cells
dendritic cells must be ___, and presentation occurs in ___
- activated
- secondary lymphoid organs
tissue dendritic cells take up antigen by what 2 mechanisms?
macropinocytosis and phagocytosis
MHC expression is ___ on immature DCs and ___ on DCs in lymphoid tissue
- low
- high
describe the location of DCs in the body
ubiquitous throughout the body
what are the 3 antigen presenting cells?
dendritic cells, macrophages, and B cells
which antigen presenting cell is primarily responsible for presenting antigen to T cells?
dendritic cells
most common and most prevalent T cell activator
dendritic cells mature though ___
antigen activation
describe the process of DC maturation via antigen activation
- immature DCs in peripheral tissues encounter pathogens and are activated by PAMPs
- TLR signaling induces CCR7 and enhances processing of pathogen-derived antigens
- CCR7 directs migration into lymphoid tissues and augments expression of co-stimulatory molecules and MHC molecules
- mature dendritic cell in T-cell zone primes naive T cells
DCs are targeted to lymph nodes by ___ binding ___ and ___
- CCR7
- CCL19 and CCL21
dendritic cells take up bacterial ___ in the skin and then move to enter a draining lymphatic vessel. DCs bearing ___ enter the draining lymph node, where they settle in the ___ areas
- antigen
- antigen
- T-cell
where do the different antigen presenting cells distribute in lymph nodes?
- DCs - T cell areas
- macrophages - all areas
- B cells - B cell areas
DCs present antigen by ___ and ___
MHC I and II
___ is critical for CD8 T cell activation
cross-presentation
what 2 ways do DCs present antigen to CD4 T cells?
- receptor-mediated endocytosis of bacteria
- macropinocytosis of bacteria or viruses
what 3 ways do DCs present antigen to CD8 T cells?
- viral infection
- cross-presentation of exogenous viral antigens
- transfer of viral antigens from infected DC to resident DC
naive T cells can enter a draining lymph node by which two routes?
- in the blood
- in the afferent lymph coming from an upstream lymph node
___ monitor antigens presented by DCs
naive T cells
naive T cell population rotates/circulates through ___, resulting in ___
- lymph nodes
- systemic antigen exposure (aka systemic ability to target infection)
T cells and DCs form immune ___
synapses
the strength of the synapse dictates whether or not the T cell will be activated
T cell activation requires which 3 signals?
- activation
- survival
- differentiation
- *process is the same for both CD4 and CD8 T cells
antigen presenting cells deliver 3 kinds of signals to naive T cells to activate them. describe.
- T Cell Receptor
- Peptide recognition
- MHC I or II
- CD8 or CD4
- Co-stimulatory Molecules
- Survival signal
- B7 family (APC)
- CD28 family (T cell)
- B7-CD28 required for T cell activation
- Cytokines
- Paracrine and autocrine
- Propagation (IL-2)
- Differentiation
- IL-2: CD8, All TH
- IL-4: TH2
- IL-6: TFH
- IL-12: TH1
- TGF-β + IL-16 + IL-23: TH17
- TGFβ: Treg
naive T cell TCR activation in the absence of co-stimulation (from ___ and ___) leads to ___
- B7 and CD28
- anergy
describe co-stimulation of T cells and antigen presenting cells, which is required for T cell activation
activation induces T cell changes in what 5 ways?
- differentiation
- clonal expansion
- changes in surface protein expression
- migration to target tissues
- effector functions
in what ways does activation induce T cell differentiation?
- CD8 T cells
- effector cells, memory cells
- CD4 T cells
- Th1, Th2, Th17, Tfh, Treg
- effector cells, memory cells