Principles of Immunology
3/28/06
“Each of us needs to be the change we wish to see in the world”
Ghandi

 ADCC
 Effector cells
 GVH reaction
 Perforin

 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

 Three types of effector T cells
 CD8 (T
C
)
 CD4 (T
H1
)
 CD4 (T
H2
)
 Each type
 Responds to different types of Ags
 Activated by different Ag presentation
 Has different effector function

 CD8
 Viruses and intracellular bacteria
 MHC I
 Cytotoxic effector cells
 CD4 T
H1
 Bacteria and parasites in APCs
 MHC II
 Effectors activate macrophages, CTLs and induce B cells to produce opsonins
 CD4 T
H2
 Extracellular bacteria and toxin producers
 MHC II
 Activate B cells to produce multiple antibody classes

 T cells pass through endothelial cells
(extravasation)
 Endothelial cells and T cells both have cell adhesion molecules (CAMs)
 Various CAMs

 Selectins
 Mucins
 Integrins
 Immunoglobulin superfamily

 Dendritic cells
 Macrophages
 B 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

 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

 Binds soluble antigens
 Constitutively expresses MHC II
 Induced to express B7

 ~5% of lymphocytes
 Nonspecific cytotoxicity
 No TCR/CD3
 Not MHC restricted
 No memory

CTL Cytotoxicity
 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