immunological tolerance

Question 1

how can tolerance be divided into

Answer 1

central and peripheral tolerance

Question 2

where does central tolerance take place

Answer 2

• thymus for T cell and bone marrow for B cells

Question 3

what happens if a B cell receptor binds too strongly to a self antigen in the bone marrow during central tolerance

Answer 3

• receptor editing
• negative selection via apoptosis

Question 4

what happens during central tolerance of T cells

Answer 4

• T cells bind to thymic epithelial cells in the cortex
• if they don’t bind at all they are eliminated by positive selection
• remaining cells binds to dendritic cells in thymus or medullary thrice epithelial cells ones which bind too stronlgy are eliminated by apoptosis
• aire a transcription factor enables the medullary thrice epithelial cells to express cell antigens from all different areas of the body

Question 5

how can peripheral tolerance be divided

Answer 5

• intrinsic and extrinsic
• intrinsic includes apoptosis, ignorance and anergy
• extrinsic include Treg cells

Question 6

what happens in intrinsic peripheral tolerance

Answer 6

• ignorance (self reactive T cells never are exposed/reach to the cells they react to e.g. if the cells it is reactive to are in eyes- immune cells don’t go to eyes)
• anergy- T cell binds to host cell however not activated due to absence of co-stimulation molecules
• apoptosis

Question 7

what happens in extrinsic peripheral tolerance

Answer 7

• T regulatory cells
• FOXP3 gene involved in development
• mutation in gene can lead to autoimmunity specifically IPEX
• releases inhibitory mediators (IL10)
• has a receptor which binds to IL2- CD25
• CTLA4 bind to CD80//86 causes negative stimulation prevent binding of CD28