Chapter 6- Effector Mechanisms of T Cell-Mediated Immunity Flashcards
what happens to a phagocyte with ingested microbes in vesicles and what T cell is used
-macrophage activation -> killing of ingested microbes
- inflammation and killing of microbes
- CD4+
what happens to an infected cell with microbes in cytoplasm and what T cell is used
killing of infected cells
-CD8+
what is the defining cytokines, target cell, host defense and role in disease of Th1
-IFNgamma
-macrophages
- intracellular pathogens
- autoimmunity; chronic inflammation
what is the defining cytokines, target cell, host defense and role in disease of Th2
-IL-4, IL-5, IL-13
-eosinophils
-parasites
-allergy
what is the defining cytokines, target cell, host defense and role in disease of Th17
- IL-17 and IL-22
-neutrophils - extracellular pathogens
- autoimmunity
what is pleiotropism meant by in properties of T cell cytokines
each cytokine has multiple biological actions
what is redundancy meant by in properties of T cell cytokines
multiple cytokines may share the same or similar biological activites
what is the function of Th1 cells
classical macrophage activation
- killing of phagocytosed bacteria through production of ROS, NO, and lysosomal enzymes
- secretion of cytokines (TNF, IL-1, IL-12, chemokines)
- increased expression of MHC and costimulators- B7 molecules
Describe Th1 cell development
- intracellular microbes + dendritic cell and NK cell
- NK cell uses IFN- gamma to act on antigen activated T cell
- dendritic cell uses IL-12 to act on antigen activated T cell
- this results in a Th1 cell
what are Th2 cells induced by
parasitic worm infections
what are the signature cytokines in parasitic worm infections
IL-4, IL-5 and IL-13
what are the functions of Th2 cells
- antibody production
- mast cell degranulation
- intestinal mucus secretion and peristalsis
- eosinophil activation
-alternative macrophage activation (enhanced fibrosis and tissue repair
what mediates the killing of helminths
eosinophils
what does Th1 cytokine IFN-gamma do
inhibits Th2 and Th17 developmental possibilities
what do Th2 cytokines IL-4 and IL-13 do
inhibit macrophage activation (M1)
what happens when a classically activated macrophage is activated by Th1
-microbicidal actions: phagocytosis and killing of bacteria and fungi
- inflammation
what happens when an alternatively activated macrophage is activated by Th2
antinflammatory effects, wound repair and fibrosis
what are immediate hypersensitivity reactions initiated by and what does it stimulate
-initiated by introduction of an allergen which stimulates TH2 reactions and IgE production
- IgE binds to Fc receptors on mast cells and subsequent exposure to the allergen activates the mast cells to secrete the mediators that are responsible for the pathologic reactions of immediate hypersensitivity
what does the balance between Th1 and Th2 cell activation determine
outcome of intracellular infections
Describe Th2 cell development
-helminths+ dendritic cells and mast cells, eosinophils
- mast cells and eosinophils use IL-4 to act on antigen activated T cell to make Th2
what are the signature cytokines in Th17 cells
IL-17 and IL-22
what are the functions of Th17 cells
- recruitment of neutrophils resulting in inflammation
- antimicrobial peptides
- increased barrier integrity
describe the development of Th17 cells
- extracellular fungi and bacteria + dendritic cell
- dendritic cell uses IL-1, IL-6, IL-23, and TGF beta to act on the antigen activated T cell
- Th17 cell
describe the mechanism of killing of infected cells by CD8+ CTLs
-antigen recognition and binding of CTL to target cell
- CTL activation and granule exocytosis
- apoptosis of target cell
what activates apoptosis in CD8+ CTLs
-perforin facilitates entry of granzymes into the cytosol
- granzymes activate apoptosis
what is the host counter defense to reduced MHC class I display on cell surfaces
activation of natural killer cells
how does mycobacteria evade CMI
inhibition of phagolysosome fusion
how does Herpes simplex virus evade CMI
inhibition of antigen presentation
how does cytomegalovirus evade CMI
inhibition of antigen presentation
how does Epstein barr virus evade CMI
inhibition of antigen presentation
- inhibition of macrophage activation
how does the pox virus evade CMI
block cytokine activation of effector cells
