immunity 2 Flashcards
2 subgroups of T cells
Helper cells and cytotoxic lymphocytes
what molecules are expressed on the surface of helper cells
CD4
what molecules are expressed on the surface of cytotoxic lymphocytes
CD8
what are the subsets of CD4 cells
helper T cells - TH1, TH2, etc…
what are TH0 cells
naive helper T cells
what allows T cell receptors to engage with other proteins
transmembrane domains
what is a TCR
T cell receptor
in the TCR, what do the alpha and beta chains associate with
CD3 molecule complex (has intracellular component called the zeta chain)
what is CD3 made of
1xδ chain
1xγ chain
2xε chains
what does that zeta chain allow
binding to turn into signalling
what do TCRs recognise
processed antigen in the form of peptides presented by MHC molecules on the cell surface
what molecules stabilise the interaction when an antigen is recognised by TCR
CD4 or CD8
3 examples of professional antigen presenting cells
dendritic, macrophage and B
what do APCs do
phagocytose dead and dying cells and pathogens, chop them up in proteolytic compartments and load the peptide fragments onto new MHC molecules
how do T cells engage APCs
via their TCR and they scan the surface of the APC for a peptide on MHC that they recognise
what happens if TCR find a peptide on MHC that they recognise
the T cell is stimulated to become an activated effector T cell, some of these also become memory cells
2 types of MHC molecules
MHCI and MHCII
what is MHCI and what does it do
major histocompatibility complex I - associates with 9-mer peptides, its present on all cells (except RBC and germ)
what is MHCI recognised by
CD8 T cells
what is MHCII and what does it do
major histocompatibility complex II - associates with 9-20mer peptides, it is only present on APCs
what is MHCII recognised by
CD4 T cells
what do CD4 (t helper) cells produce
cytokines
what influences which antibody isotype is produced
the type of cytokine
what can cytokines activate
granulocytes, macrophages, NK cells
what influence do T helper cells have on cytotoxic t cells
the cytokines make the cells have better memory and make them better effector cells
what cytotoxins do CD8 cells produce (3)
perforin, granzyme, Fas
what cytokines do CD8 cells produce
IFNγ , TNF-β , TNF-α
what does granzyme do
enters the cell, cleaves a caspase which triggers apoptosis
what does FAS ligand engagement do
activates a caspase and triggers apoptosis
CD8 T cells and tumour cells
CD8 T cells produce cytotoxins that kill tumour cells with tumour antigens
CD4 cells and tumour cells
CD4 is stimulated by APCs or other stresses that happen in tumours
what does IFNγ do to tumour cells
it causes an up regulation of MHC so it is easier for CD8 cells to recognise and kill them
correlation between immune cells and cancer survival
there is a direct correlation between number of immune cells you have (CD8 T cells) and how long you will survive
what is immunosurveillence
the immune system is capable of recognising that changes that occur in cancer cells and eliminates those cells e.g. CD8 cells can recognise cancer antigens and sometimes neo-epitopes
what are neo-epitopes
new epitopes
what is a stress pathway
cells which have gone wrong up regulate many mechanisms and the immune system is made aware of this
immunoediting - elimination
the immune system recognises new tumour cells and eliminates them
immunoediting - equilibrium
some tumour cells are not recognised and so keep mutating - eventually becoming recognised - therefore an equilibrium stage occurs
immunoediting - escape
some cells mutate to grow at a faster rate so have reached the escape phase and eventually give rise to end stage tumours
3 E’s of immunoediting
elimination, equilibrium, escape
