T cells vs B cells Flashcards
Th2 cytokines fx
Work against helminths
Where in lymph node do macrophages and dendritic cells aggregate
Medullary sinus (most central)
Where in lymph node do T cells aggregate
Paracortical area
Where in lymph node do B cells aggregate
Primary lymphoid follicle (germinal centres can develop here)
Describe positive selection + where does it occur
Thymocytes that don’t recognise recognise MHC-1 or MHC-2 undergo apoptosis
Occurs in thymic cortex
Describe negative selection + where does it occur
Thymocytes that recognise self undergo apoptosis
Occurs in thymic medulla
Where in thymus do T cells develop
T cell progenitors enter thymus through HIGH ENDOTHELIAL VENULES
They then migrate to SUBCAPSULAR REGION
As they mature, they move further into CORTEX as they start to express specific receptors
After positive and negative selection, T cells migrate from cortex to MEDULLA
What receptors do a developing thymocyte express
CD3, CD4, CD8 (all)
Thymocytes that interact with MHC-1 or MHC-2 develop into what kind of T cells
MHC-1: CD8
MHC-2: CD4
Define central tolerance
Negative selection in thymus
To discriminate self from non-self
Define peripheral tolerance
Prevents over-reactivity of immune system to environment
Define peripheral tolerance
Prevents over-reactivity of immune system to environment
Self reactive T cells that escaped negative selection are deleted in peripheral tissue by nTreg cells or deactivated by dendritic cells
CD22 (expressed by B cells) dampens BCR activation
Receptors expressed by B cells
CD22: dampens BCR activation
What are B cell receptors known as when they are freely floating
Antibodies
How is B cell receptor diversity generated
- VDJ recombination
- imprecise VDJ joining (junctional diversity)
- random addition of nucleotides
- class switching (IgG to others)
- somatic hypermutation (selects B cells with highest affinity for Ag)
BCR: heavy and light chains
TCR: alpha and beta chains (same mechanism)
