L17 effector cells Flashcards
what is clonal selection
selective expansion of lymphocytes that interact with antigen
what are cytotoxic lymphocytes also known as
CD8 effector cells (T Cells) that have undergone proliferation and activation by a DC
what are CTL used for
serial killers of tumour cells
they engage, disengage and continue to kill other cells
how are proteins produced by viruses in infected cells displayed on MHC I
The proteins being made by the virus within the cell are sometimes released to the cytoplasm and loaded onto MHC
where are CTL activated and by what
lymph or spleen
by a DC
what are the ‘weapons’ of CTL
granzyme
perforin
CD95 ligand
when are perforin and granzyme secreted by a CTL
when it recognises MHC peptide
how does perforin work?
makes pores in the lipid bilayer by forming polymeric cylindrical structures allowing granzyme to enter the cell
what does granzyme do
cleaves target cell proteins which initiates apoptosis
what does CD95 ligand do?
bind to CD95 triggering apoptosis because enzymes like caspases are being activated which initiate apoptosis
what attracts CTL to an area of the body
inflammation
what happens during apoptosis
cell components are being degraded, doesn’t explode
uses energy
cell shrinks
what happens to the fluid and membrane of cells during apoptosis
form apoptotic blebs
what happens to apoptotic blebs
consumed and digested by macrophages or neutrophils (phagocytes)
how do viruses downregulate MHC I
production of proteins which stop MHC reaching the surface
what happens if a cell does not express or only has lo levels of MHC I
natural killer cells are activated
What two receptors do NK cells use to activate apoptosis in infected cells
inhibiting
activating
what does the activating receptor of NK cells do
binds to living cells and lets the NK know there is a cell there
what does inhibitory receptor do
binds to MHC I
lets the NK know that the cell is expressing MHC I
what does an NK do when there is no MHC
the activating receptor receives a positive signal and it builds up and it releases cell-killing proteins (perforin, granzyme)
what happens during type 1 hypersensitivity
B cells are more prone to class switch to IgE
what happens during type 1 hypersensitivity
B cells are more prone to class switch to IgE
what happens during an allergic reaction
mast cells bind two IgE (that are sensitive to non-threatening antigen) antibodies to the surface through FC receptors
antigen crosslinks the antibodies which stimulate mast cells to produce histamines, serotonin (allergic mediators)
what are Tregs
type of CD4 helper cells that secrete immunosuppressive cytokines
what is peripheral tolerance
DC cells lacking CD80 which stops co-stimulation
what happens during neonatal tolerance
a wave of Tregs is produced to suppress the cytokines
infants are already immunocompromised
central tolerance is highly active while neonatal
what happens during central tolerance of B cells
self antigen is passed over maturing B cell in bone marrow
