T4L9 - T cells Flashcards
CD4 is a
helper
CD8 is a
cytotoxic
T cell function [2]
Direct immune response: CD4 orchestrate response
Kill virally infected cells: Antibodies cannot cross cell membrane of virus infected cells and CD8 recognises and kills them
T cell antigen recognition [3]
T cells are antigen specific
Antigen recognised is peptide processed from intact antigen
Peptide presented by major histocompatibility molecule
T cell generation
T cell precursors from BM
Gestation -> migrate from BM to thymus
Thymus specially adapted for education of thymocytes: Select useful and remove self reactive
Class I pathway - antigen presenting 1
- Virally infected cell is synthesising viral proteins
- Pass through ER and Golgi -> cytoplasm
- Assembled into virus particles
Class I pathway - antigen presenting 2 [3]
Sample of protein in cytoplasm passed into proteasome - tubular organelle lined with enzymes
Proteins degraded into peptides and transported back into ER by TAP transporter
In ER, the peptides are loaded onto MHCI molecule
Class I pathway - antigen presenting 3 [2]
CD8 with correct receptor can recognise peptide as foreign and kill target cell
MHCI groove contains self peptide in healthy cell
Genital ulcer
Breach in mucosa where infected epithelial cells have been killed
CD4 [5]
Antigen presented by MHC class II molecule
Antigen only presented by specialised antigen presenting cells
Antigen taken from extracellular space
Macrophage and dendritic cells sample antigens from extracellular space by endocytosis/phagocytosis
Antigen degraded into peptides and loaded onto MHCII
CD4 and B cell maturation
• B cells recognise antigen by antibody receptors and internalise it
• Presented to T cells as peptide with MHCII
• T cells provide signals to B cells via cytokines and juxtacrine signalling
This stimulates the T cell, which then stimulates the B cell appropriately
CD4 and macrophages
• Macrophage infected with mycobacterium tuburculosis – unable to kill organism
• TB peptides presented with MHCII on surface
TB-specific CD4 T cell recognises TB, and provides help to macrophage (cytokines and juxtacrine signalling)
TH1 [2]
Cell recognise complex of bacterial peptide with MHCII
Activate macrophage
T cell memory
Primary: Naive CD4 and CD8 response
Clonal selection of most responsive
Resolution: Most antigen-specific CD4 and CD8 cells die off but some remain as memory
Secondary: Pre-existing memory T cells respond more rapidly and robustly
Innate overview [4]
Receptors are germline encoded
Receptors are the same on all cells that express them
No memory
Quickly
