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Principles of Immunology
T Cell-Mediated Immunity
3/28/06
“Each of us needs to be the change we wish to see in
the world”
Ghandi
Word/Terms List
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ADCC
Effector cells
GVH reaction
Perforin
T Cell-mediated Immunity
Principal function-Response to
intracellular pathogens and cells
expressing foreign antigens
Recirculation-Naïve T cells circulate
between the blood stream and the
lymphatic system
Antigen presentation-Naïve T cell
cells only respond to APCs
Priming of T Cells
 Three types of effector T cells
 CD8 (TC)
 CD4 (TH1)
 CD4 (TH2)
 Each type
 Responds to different types of Ags
 Activated by different Ag presentation
 Has different effector function
T Cell Effector Types
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CD8
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CD4 TH1
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Viruses and intracellular bacteria
MHC I
Cytotoxic effector cells
Bacteria and parasites in APCs
MHC II
Effectors activate macrophages, CTLs and induce B cells to
produce opsonins
CD4 TH2
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Extracellular bacteria and toxin producers
MHC II
Activate B cells to produce multiple antibody classes
T Cell Adhesion
 T cells pass through endothelial cells
(extravasation)
 Endothelial cells and T cells both have
cell adhesion molecules (CAMs)
 Various CAMs
Cell Adhesion Molecules
 Selectins
 Mucins
 Integrins
 Immunoglobulin superfamily
APCs
 Dendritic cells
 Macrophages
 B cells
Dendritic Cells
 Antigen presentation is sole function
 Antigenic uptake is followed by
migration to lymph nodes
 Expression of MHC I, MHC II and B7
 Loses phagocytic property
 Secretes chemokines
Macrophages
 Involved in both innate and adaptive
immunity
 May destroy pathogens or present Ag
to T cells
 Expression of MHC I, MHC II and B7
 Scavenges dead cells
B Cells
 Binds soluble antigens
 Constitutively expresses MHC II
 Induced to express B7
NK Cells
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~5% of lymphocytes
Nonspecific cytotoxicity
No TCR/CD3
Not MHC restricted
No memory
CTL Cytotoxicity
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Conjugate formation
Membrane attack
Dissociation
Target cell death
Conjugate Formation
 Cell adhesion
 Recognition of MHC I:Ag on target
cell
Membrane Attack
 Granules in CTLs
 Perforin
 Granzymes
 Exocytosis of granule contents
 Perforin action similar to C9
 Granzymes act as nucleases
 Fas ligand to Fas triggers target cell death
Dissociation and Target Cell Death
 CTL interacts for about five minutes
 Dissociates and can conjugate with
other target cells
 Target dies after several hours
Antibody-Dependent Cell-Mediated
Cytotoxicity
 NK cells, macrophages, neutrophils
 Bind to Fc region of Ab
 Multiple cytotoxic mechanisms
Graft vs. Host Reaction
 Immunocompromised recipient
 Lymphocytes of donor attack
allogeneic antigens of recipient
 Splenomegaly