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28 terms

Cellular Immunity

STUDY
PLAY
CD3
Expressed on all T cells and is needed as a signal transducer for the T cell receptor
antigen processing
peptides are generated from larger polypeptides
CD8 T Cell
Killers
directly attack virus infected cell
recognize MHC I
CD4 T Cells
helper T cells
T helper 1 - recognize macrophages
T helper 2 - recognize B cells
recognize MHC II
MHC
control T cell mediated immune responses
determine the fate of transplanted tissues
HLA molecules encoded in MHC
MHC I cells
almost all nucleated cells
excluding brain and erythrocytes
process antigens from INSIDE the cell
MHC II cells
antigen presenting cells
B cells
Macrophages
Dendritic cells
take up antigens from OUTSIDE cell
How are MHC genes inherited?
as Haplotypes
genes are co-dominant
MHC restriction
a given T cell receptor will recognize its peptide antigen only when the peptide is bound to a particular form of MHC molecule.
T cell maturation
Start with double negative progenitor cell (lacks CD4 and CD8)
End with double positive CD3+
Positive selection
Weak recognition of MHC I/II + peptide by immature T cell
determines expression of either the CD4 or CD8 molecule
Death by neglect
Immature T-cell does not recognize MHC + peptide
undergoes apoptosis
Negative selection
Immature T cell binds too strongly to MHC + peptide
undergoes apoptosis
selectins
Adhesion molecules
allows lymphocytes to home to lymph nodes or to sites on infection
ICAMs
Allows T cells to "talk" to APCs
T cell activation and signal transduction
PKC activates transcription factor NKfB
Calcineurin activates transcription factor NFAT
NKfB & NFAT start production of cytokines
CD80 and CD86
molecules on APC that binds CD28 on naive t cells and deliver necessary co-stimulatory signal to t cell
Co-stimulation
delivers required second signal for T cell activation
1) Binding of TcR and CD4 to MHC class II delivers signal to T cell.
2) Clonal expansion of T cell can occur only after second signal is delivered by CD80/86:CD28 interaction.
down regulated by CTLA4
IL1
Source: APCs
Effect: inflammation
IL2
Source: Th1 cells
Effect: T cell growth
IL4 and IL5
Source: Th2 cells
Effects: antibody production, class switching
IL10
Source: Th2 (Treg)
Effects: inhibits Th1
IFN gamma
Source: Th1
EffectL inhibits Th2
TNF
Source: Th1
Effect: inflammation
CD8 T cell effector molecules
Perforin, granzymes, fas
Response: cytotoxic
CD4 T cell effector molecules
TNF, IL2
Response: down regulates Th1, inflammatory, humoral
T-helper 1 cells
Driven by IL12 and IFN-gamma
Produce IFN-gamma
Host defense against intracellular microbes
inflammation
Cellular immunity (CD8 T cells, macrophages)
T-helper 2 cells
Driven by IL4
Produce IL4, 5, 10, 13 and TGF-ß
host defense against helminths
allergic reactions
Humoral Immunity (B cells)