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T CELL (FUNCTIONS (Immune mediated cell death (CD8+ T cells directly kills…
T CELL
FUNCTIONS
Immune mediated cell death
CD8+ T cells directly kills virus-infected / cancer cells
CD8+ T cells utilise cytokines to recruit other cells
CD4+ T cells indirectly kill cells that are foreign
Regulatory T cells
distinguish invading cells from self
prevents autoimmune response
used by cancer cells to prevent recognition / immune response against tumour cells
CD4+ : Helper T cells
maturation of B cells into plasma / memory cells
activated when presented with peptide antigen by MHC II molecules on APC ( dendritic cells )
CD8+ : Cytotoxic T cells
destroy virus-infected cells / tumour cells / transplant rejection
activated when presented with peptide antigen by MHC I molecules on APC ( on all nucleated cells )
ACTIVATION
FIRST SIGNAL
Antigen specific
MHC II:TCR peptide bond on CD4 T Cell
MHC I:TCR peptide bond on CD8 T Cell
SECOND SIGNAL
amplification by co-stimulatory molecules
CD28:B7
CD40:CD40L
THIRD SIGNAL
cytokines production by antigen-presenting cells
T helper cells exposed to IL-12 or IFN will become TH1
IL-2 production leads to proliferation of T cells
T helper cell exposed to IL-4 will become TH2
IL-2 produced by CD4 T cell activates CD8 T cell
RESPONSE
T cell secretes effector molecules onto surface of target cell
CD4 T cells
TH2 cells
Cytokines: IL-4, IL-5,IL-10, IL-13, TGF-β
TH1 cells
Cytokines:IFN-γ, GM-CSF, TNF-α, LT, IL-3
TH17 cells
Provide protection against extracellular bacteria & fungi
T Reg cells
Control the immune response to self and foreign particles (antigens).
Help prevent autoimmune disease
CD8 T cells
Cytotoxic T cells
Cytokines
Lymphotoxin (TNF-β)
Induce gene expression of MHC
Responsible for establishment and maintenance of lymphoid structures
IFN-γ
Activate macrophage then increase their phagocytic activity
Induce MHC II expression and promote the processing and presentation of antigens
Cytotoxins
Perforin
Form pores to provide access of anti-microbial granule proteins to their targets to cause cytolysis
Granulysin
Antimicrobial activities- Destroy microbes
Granzymes
Induce apoptosis
Kill bacteria
Inhibit viral replication
