Week 4 Flashcards
Positive selection
Ensures the cell works and that it matures
Negative selection
Removes cells that are reactive to the body
Role of the CD4 cell
Provides growth factors / enzymes
CD8 role
Kills the antigen
What cells fight viruses
Th1 response, CD8 T cell and macrophages
What cells fight extracellular bacteria
TH2 , B-cell and phagocytes
Parasitic response
Th2 – IgE mediated
IgE producing B cells & Mast cells and eosinophils & basophils
Infection at the mucosal layer
Helper cell: Th17 response
– Effector cells: Neutrophil and monocytes
How are CD4 cells activated
Cell engulfs pathogen
Breaks it into enzymes
Antigen presenting cell puts peptides on surface using mhc class 2 molecule
CD4 that hasn’t recognised it finds the APC that has the antigen and binds to it (1st signals)
CD28 on t cell and b7 molecule on dendritic cell (2nd signal) activates it
CD8 t cell activation
Cell recognises antigen with mhc class 1 molecule
TCR on naive cd8 t cell binds to mhc molecule, 1st signal
CD28 and b7 on dendritic cell bind for 2nd signal
Difference betwenn CD4 and CD8
cd4 is a helper cell cd8 is the killer
cd4 uses mhc class 1 , cd8 uses 2
cd4 activates immune cells, cd8 excretes enzymes
cd4 controls IS cd8 kills antigen
Antigenic drift
Antigen changes its receptors or its genes
Activated immunity
Results when lymphocytes respond to a vaccine
or toxoid – memory is induced
passive immunity
Occurs when preformed antibodies are given,
resulting in temporary immunity
Toxins are neutralised by
Antibody
