Effector T-lymphocytes Flashcards
(25 cards)
What kind of response is carried out by T lymphocytes?
Cell-mediated
What are the three main types of T cell
Naive
- no antigen encounter
Effector
- post antigen encounter, proliferation occurred
Memory
- post encounter, ready to respond to future infection
Why is a cellular response needed?
Intracellular pathogens, humoral can’t affect
Antibodies can be evaded by evolution
T cells can ingest and kill
How are T cells activated?
Once made in spleen - receptors added
DC presents antigen on MHC that binds to CD receptos
T cell then detects antigen and proliferates
Why do T-cells get activated in the lymphoid tissue?
They are naive and hence cannot enter non-lymphoid tissue - cirulate in blood and lymphoid organs
Only once become effector
What are the 3 phases of cell mediated immunity?
Induction - DC collects material and presents
Effector - MHC:TCR interact, T cell now effector, sees pathogen and deads it
Memory - Effector pool contracts to memory
What are the signals needed to activate a naive T-cell
Antigen recognition
Co-stimulation
Cytokine release
What are the main effector functions of T lymphocytes?
Cell-mediated cytotoxicity - CD8
T helper cells - CD4
What are the roles of T-helper cells?
macrophage activation
Delayed type hypersensitivity
B cell activation
Regulation
How do CD8 Cytotoxic t lymphocytes destroy target cells?
recognices MHC 1 peptide complexes
Immature CD8 cells are activated by this and can then perform effector cells
Specific recognition by cells causes polarisation, leading to release of GRANULES
Which granules are used for causing cell death and how do they do this?
Perforin - pores in CM
Granzymes - serine protease - apoptosis
Granulysin - apoptosis
How else can cd8 cells cause cell death?
Fas-FasL interaction
FasL on CD8 interacts with Fas protein on target
- cascadeactivates apoptosis
how are cd4 cells helpful?
naive cells can be differentiated into distinct subsets
What are the subsets of T helper cells?
T helper 1
T helper 2
Follicular T helper
T helper 17
T reg
What are the functions of Th1?
Produce IF-gamma - activates macrophage
What are the functions of Th2?
IL-4, 5, 13
Allergic response - eosinophil (5), B cell (4)
What are the functions of Tfh?
IL-21 - stay in B cell follicles
Generation of isotype-switched ABs
What are the functions of Th17?
IL-17 for autoimmune disease
Bacterial control
What are the functions of Treg?
T cells that regulate activation of over T cells
Maintain tolerance ot self antigen
prevent autoimm
How are macrophages activated?
Th1 release IFN-gamma
More macrophages active, means more CD40 and TNFalpha recepotrs, more TNF secreted, which acts with IFNgam to put on antimicrobial effector mechanisms
What is delayed type hypersensitivity?
Defense against intracellular pathogens
If source of antigen not gone, granuloma formation and injury formed without protection - hypersensitive
Sensitisation
Effector
HOw do T cells exhibit memory?
Once exposed and responded to antigen, they contract, becoming memory
What is T cell exhaustion?
CD8 pool reduces to prevent excess damage
Problematic due to incomplete infection clearing - HIV CMV
What are the good and bad things T eff cells do
Clear pathogen
Autoimmunity
Rejection of transplant
