Immune Recognition and Immune Tolerance Flashcards
What are the 6 main players in immune response?
CD4 t-cell CD8 t-cell B-cells dendritic cells macrophages neutrophils
Where do T-cells and B-cells develop?
T-cells = thymus B-cells = bone marrow
How do we establish immune tolerance?
Starts with thymic education
Thymocytes express functional t-cell receptor to learn if CD4 or CD8 is more appropriate
T-cell receptor genes arranged and paired together
T-cells that form functional alpha beta receptor make it to the cell surface
cells with functional ab receptor express co-receptors
in positive selection they make sure t-cell receptors can bind to MHC class 1 and 2 molecules with at least weak affinity (occurs in thymus cortex)
if t-cell has weak affinity for MHC2 then it stops expressing CD8 and becomes a CD4 t-cell and can no recognise MHC2
What is negative selection?
Elimination of t-cells which have particularly high affinity for self peptide and self MHC. you cant have too high of an affinity
What are the 3 criteria for thymic education?
Functional TCR
TCR interacts with self MHC
TCR cannot have a high affinity for self antigen
What is Anergy?
Where you receive signal 1 without signal 2 which means the t-cell remains in circulation
What are the two types of regulatory t-cells?
nTreg - respond to self antigens
aTreg - protection from autoimmunity
How migration in immune response works?
Cytokines and chemokines upregulate adhesion molecules that go to lymph node
chemokines secrete for an increase in the migration of naïve t-cells
t-cells move to lymph node which increases its size
T-cells then encounter MHC present on the surface of APC
How CD4 t-cells are activated?
Signal 1 - recognies MHC1 complex on dendritic cell
signal 2 - costimulatory molecules from APC to T-cell
signal 3 - cytokines instruct t-cell to polarise into CD4
Cytokines differentiate CD4 into its different pathways
How to activate CD8 T-cells?
Th1 provide cytokine help to cytotoxic t-cells so CD8 can proliferate and differentiate
Migration of effector T-cells?
They go to inflamed tissue
find MHC molecules on APC
if they have affinity for MHC they enter effector function
CD4 cells provide help by secretion and CD8 kill pathogen
some t-cells move out of the tissue and become cells that maintain immunological memory
What are the two sites b and t cells are retained?
Lymphoid organs and in the tissues themselves
