IIH L13-15 T cell block Flashcards
What is tolerance? L13
Process of eliminating or neutralising self-reactive lymphocytes
What cell types are considered thymus stromal cells? L13
Cortical and medullary epithelial cells and dendritic cells
What type of thymocytes are in the cortex? L13
Immature
What type of thymocytes are in the medulla? L13
Mature
What happens in the thymic cortex and what is the predominant cell type? L13
TCR gene rearrangement and (+) selection
Reticular epithelial cells
What happens in the thymic medulla and what is the predominant cell type? L13
(-) selection
Thymic epithelial cells expressing the AIRE gene which allows peripheral tolerance
What is (+) selection? L13
Allows T cells that recognise foreign antigen to mature, done by cortical epithelial cells. T cells that fail to recognise antigen die by neglect
What is (-) selection? L13
Removes potentially auto-reactive T-cells that recognise self-peptides; mediated by medullary dendritic cells
What cell type is present at the cortico-medullary junction in the thymus and what is its function? L13
Macrophages prevent damaged/dying cells from passing to the medulla
What percentage of T cells survive the selection processes in the thymus? L13
5%
Where are the two sites of immune ignorance in the body? L13
Eye and testes
What is the function of T-reg cells? L13
Prevent auto-reactive T cells from causing damaging immune responses
What is clinical autoimmunity? L14
Consequence of loss of tolerance
What are the three mechanisms for loss of tolerance? L14
Sites of ignorance (testes and eye)
Failure of Treg cells
Inappropriate antigen presentation
What are some ways that autoantibodies can cause damage? L14
Lysis of self cells
Immune complex formation
Blockade of receptors for physiological ligands e.g. Myaesthenia Gravis and Pernicious Anaemia
Stimulation of cell surface receptors e.g. Graves disease (ABs imitate TSH)
What is Goodpasture’s syndrome? L14
Autoantibodies against lung and kidney basement membranes
What happens in rheumatoid arthritis? L14
Systemic inflammatory disease
Autoantibodies against Fc portion of IgG
Anti-CCP antibodies
Which cells are principally infected by bacterial pathogens? L15
Monocytes and macrophages
How do bacterial pathogens avoid the immune response? L15
Rupture early phagosome and escape into cytosol
OR
Block fusion of phagosome and lysosome
Which cytokines are released by dendritic cells that promote activation and differentiation of naive CD4 and CD8 cells? L15
IL-12 and IL-18
What do CD4 Th1 cells release in response to bacterial pathogens? L15
IFNγ and TNFα
What does IFNγ promote? L15
Macrophage activation
When macrophages are activated what is there increased expression of? L15
MHC I & II
CD40
CD80
ROS
What primes Th1 cells? L15
MHC II presentation
