Cellular Immunity Flashcards
Where do T lymphocytes originate from
Bone marrow and mature in thymus
What’s first evidence a T cell is going to form
2 coreceptor molecules (CD4+ and CD8+)
And T cell receptor
What is CD8+
Cytotoxic T cell can recognise non self (viral infected cell) and kill it
What is CD4+
Helper cell that recognises same type of antigen (MHC?) and produces numerous cytokines that provides signal for immune response
What’s 4 main types of helper cells
Treg - dampens down immune response so u don’t undergo hyper immune response
Th1-cellular response
Th2-antibody response
Th17- inflammatory response
Why is thymus largest at birth then shrinks
Because it’s active before birth as the entire T cell repertoire is generated before you’re born
What do T cells learn in thymus
To recognise self MHC molecules. Most T cells die from neglect so don’t mature
What’s human leukocyte antigens
Group of proteins on surface of cells that recognise self/non self antigens
How does CTL kill non self tumours
Cytotoxic T cells (CTL) reacts to ur own cells when there’s change in MHC (when neo antigen) is expressed. Become activated and release granules to kill
What’s self
Antigen encoded by MHC
What’s non self
Antigen encoded by virus
What is contacted by alpha helix which sits on top of MHC molecule
T cell receptor. When self peptide on MHC molecule changes to non self peptide then T cells recognise the difference»_space; starts adaptive immune response
What does CD4 and CD8 cells recognise
CD4 - helper T cells, Antigens in MHC class II
CD8 - cytotoxic T cells, antigens in MHC class I
How does CD4 and CD8 initiate T cell signalling
Has kinases associated with cytoplasmic tails and initiate signalling through phosphorylation
What’s T cell help in CD4+ helper function
When T cells proliferate and produce cytokines. Helps immune response
Mechanism required for B cells to make antibodies
What’s killing
CD8+ cytotoxic kills viral infected cell by producing granzymes and perforins that punch holes in cell membrane and destroy cell viability
Summary MHC class 1
Antigens from inside cell primarily through viruses.
Responding T cells = CD8
Function is to kill - cytotoxic
Summary MHC class II
Expressed primarily on antigen presenting cells (extracellular) engulf bacteria > broken down to stimulate CD4 cells to create help
What’s MHC polymorphism
MHC amino acid sequence varies greatly.
Hundreds of variations at each MHC locus.
Polymorphism restricted to protein domains that form peptide groove.
12 total polymorphic molecules expressed on ur cells and no one shares exactly same MHC profile apart from identical twins
Why is MHC polymorphic
It’s a form of natural selection to diversify populations response to new pathogens
Consequences of MHC polymorphism
- Tissue transplant is difficult as donor MHC is non self and rejected by recipients T cells. Requires tissue typing for donor selection
- MHC polymorphisms strongly linked to autoimmune diseases
