T-cell development Flashcards
Humoral immunity definition
B-cell response resulting in antibody production
Cell-mediated immunity definition
T-cell response
T-cell maturation
T-cells are educated in the thymus to prevent autoimmunity
They must undergo positive and negative selection before they are released into the blood
T-cell positive selection
Must bind MHC-peptide complexes
Facilitated by cortical thymic epithelial cells (cTECs)
T-cell negative selection
Must ignore self antigens
Facilitated by medullary thymic epithelial cells
Naive T-cells
Have not encountered antigen since leaving the thymus
Effector T-lymphocytes
Have acquired effector functions and are able to enter peripheral tissues after antigen binding
Memory cells
Remain in a resting state after the pathogen has been destroyed
Immunological synapse
When naive T-cells encounter complementary antigen, they stop migrating and bind, forming an immunological synapse
This synapse is stabilised by adhesion molecules such as ICAM-1
T-cell antigen recognition
The TCR requires co-stimulation for full activation
-CD80/CD86
These bind to CD28 on the TCR
Expression of co-stimulatory molecules is induced by microbial products
Lack of co-stimulation results in anergy
T-cell signal transduction
When binding to the TCR has occured, the signal is transmitted intracellularly
This occurs when kinase Lck phosphorylates and activates ITAMs
T-cell clonal expansion
Proliferation of T-cells is induced by cytokines
This is mainly IL-2, which acts via an autocrine mechanism
T-cell differentiation
During an immune response, further cytokine signals induce T-cells to differentiate into different types of effector cells
Th1 cells
Stimulated by: IL-12, IL-16 & IFNy
Respond to intracellular pathogens & are pro-inflammatory
Effector cytokines = IL-2, TNFa, IFNy
Th2 cells
Stimulated by: IL-4
Cause mast cell, eosinophil and B-cell activation, respond to helminthic parasites
Stimulate IgE production
Effector cytokines = IL-4, IL-5, IL-13
