Lecture 13 Flashcards
(27 cards)
What is it he difference between naive and effector T cells?
Naive: have no encountered antigens (foreign peptide MHC complex) in periphery lymph
Effector: antigen experienced, can function by kill or producing cytokines
Naive—> activation—-> effector
T cells in the peripheral tissue have ____ education in the _____ to recognize _____ peptides by ____
Undergone—-> thymus—> foreign —-> self MHC
How to T cells enter lymph nodes?
Via high enthotehial venues (HEV)
T cells migrate thru 2nd lymphoid tissues sampling ___ on dendritic cells, then what happens?
MHC
When meets right APC—> gets activated
What are the co stimulators molecules for T cell activation?
Why are they important?
B7 expressed on professional APC are co stimulators molecules & binds to CD28 expressed on surface of T cells
Required for proper activation of naive T cells
What are required to direct naive CD4 T cells to become fully differential to effector cells?
Signal1–> activate via MHC peptide complex, which determines specificity
Signal 2–> survival , costimulates like B7 interacting with CD28
Signal 3–> differation—> cytokines
How does TCR recognize?
What does TCR MHC peptide complexation determine?
Antigen in the form of a peptide bound to an MHC complex
Antigen specificity
Purpose of MHC in thymus & periphery?
Thymus: support T cell development & shape the mature T cell
Periphery: present antigens to T cells leading to activation
What are memory cells?
Previously knew their antigens & have been activated & done their job
They are waiting a re infection by the same pathogen & can be activated to clear infection
What are the major differences in the requirement of naive vs effector/ memory T cells to proliferate ?
Naive need:
Signal 1–> TCR & MHC peptide complex
signal 2–> co stimulators w/ CD28 ( on T cell form naive) & b7 ( on dendritic cell)
Effector/ memory:
TCR & MHC antigen activation
DO NOT NEED co stimulation
What is the difference between MHC 1 (all cells) and MHC 2?
Type of antigens, location, examples, responding cells?
Antigen:
1: intracellular
2: extracellular
Location:
1: cytosol
2: endsome
Examples:
1: viral proteins
2: extracellular bacteria
Responding:
1: CD8 T cells
2: CD4 T cells
Examples:
Differences between CD8 and CD4?
What are the functions?
How do they differ in their antigen recognition characteristics?
CD4: recognize MHC class 2
Coordinate immune response & alert other immune cells
CD8: recognize MHC class 1,which presents intracellular antigens
Infect & kill cells
What is MHC class 1 pathway?
A chain binds calnexin until B2 microglobin binds
A:B2 complex released—> binds chaperons + TAP
DRIPS are degraded by proteosome
Peptides delivers to ER via TAP
Peptide bind MHC
Pathway of MHC 2?
** not expressed in every cell***
Must endocytose antigens with acidity, which will degrade it to a peptide
-need chaperone
What are the steps involved in the initiation of T cell based immune respones?
T cells bind to APC
TCR specifically recognizes antigens found in NHC
Proliferate & differtiate into effector cells
When infection is over—-> many cells will die OR some will last as memory T cells
How does immune system ensure that peptides are derived from a diverse array of pathogens?
Antigens are processed & presented by MHC and MHC can present many peptides
T cells w diverse T cell receptors are produced that can recognize any peptide
How do cytotoxic T cells (CTL) kill infected cells?
Perforin forms pore in target
Granzymes are delivered, enters cell to signal cascades!!
Granzymes B cleavage
Capsases activated
Degration —> apoptosis
Induces apoptosis of target cells via secretion of perforin & granzymes that are mediators for cytolysis
Apoptosis causes no inflammation , necrosis causes inflammation
What are professional APC?
APC expressing co stimulators (B7)
Dendritic cells, macrophages, B cells
How does cytotoxic T cells kill avoid killing cells not infected?
MHC peptide recognition on target cells via secretion
What do naive T cells produce upon professional APC stimulation?
IL2
Activation—> proliferation—> clonal expansion
What happens if a naive T cells bind meets APC w no co stimulators molecule?
What happens if only Co stimulators but not TCR: MHC complex?
Does not recognize peptide —> react to self proteins—> anergic
No effect on T tell
Cytokines determine the fate of T cells, turns them into?
Cytoxic T cells (cd8, MHC class 1 prohibited)—> kill target cells
Helper T cel (CD4, MHC class 2 prohibited)—> stimulate B cells via secretion
regulatory T cell
Th1 (IFN-y) is a effector CD4,
what cytokines and function does it have?
Activates macrophages inducing cell mediated immune responses
CD4 effector cell: IL4 Th2
Kind of cytokine & function?
Humoral immune response
Helps B cells to produces Ig,
activated eosinophils & mast cells &
induces Th2 generation.
IL 5 & 13 produce B cell growth
