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ANTIGEN PROCESSING AND PRESENTATION - MHC COMPLEX - Coggle Diagram
ANTIGEN PROCESSING AND PRESENTATION - MHC COMPLEX
THE T CELL ACTIVATION CODE
T cells cannot recognise antigens in its native forms
antigens must be presented by APCs to be activated and mount an effective response
FIVE SIGNAL CODE FOR T CELL ACTIVATION
CODE 3
T cells can express co-receptors [CD4 and CD8]
mature T cells (Tc or Th).
MHC class restriction
CODE 4
T cells must express co-stimulatory molecule.
The ligand pair will be expressed by the APCs
control. Defective = no T cell activation
CODE 2
antigen must be presented via MHC molecules by APCs
self/non-self recognition
CODE 5
T cells respond to cytokines produced by APCs
another layer of control.
communication
CODE 1
T cells must express TCR on its surface
no TCR = no T CELL
TCR AND APCs
TCR COMPLEX = FUNCTIONAL RECEPTOR
TCR αβ heterodimer
antigen recognition
TCR associated with two CD3 heterodimers
TCR associated ζ chain
TCR-mediated signal transduction via ITAMs
(immuno-receptor tyrosine-based activation motifs
mediate T cells functional response after antigen recognition
ANTIGEN PRESENTATION
APC = SPECIALISED HOST CELL
antigen (Ag) fragment
peptide from pathogen
MHC Ag complex
recognised by the T cell antigen receptor TCR
MHC molecule
either MHC class I or II
MHC MOLECULES AND STRUCTURE
CLASS I
found on all nucleated cells and dendritic cells in secondary lymphoid tissue
present endogenous peptides/viral antigen fragments to Tc cells which express CD8+
CD8 molecule on the Tc cell docks to MHC I protein
if its TCR recognises the viral derived epitope
Tc cell induces target cell or dendritic cell to undergo apoptosis
so they mediate cellular immunity
also present host endogenous proteins but they dont activate an immune response
CLASS II
only found on specialised/professional APCs: dendritic cells, macrophages, B cells
These cells uptake pathogen antigens of exogenous origin, process them and present antigens fragments to Th cells
