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CMB2004 Questions and Answer | Latest Update 2024/2025

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Why do we need immunological tolerance? ~~> This allows us to get random generation of the repertoire of BCR and TCR This means self-reactive specificities will be made Without tolerance, we will get self destruction How do lymphocytes become tolerant? ~~> Central tolerance - they enc...

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  • September 15, 2024
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1 | P a g e | © copyright 2024/2025 | Grade A+




CMB2004 Questions and Answer |
Latest Update 2024/2025
Why do we need immunological tolerance?


~~> This allows us to get random generation of the repertoire of BCR and

TCR

This means self-reactive specificities will be made

Without tolerance, we will get self destruction




How do lymphocytes become tolerant?


~~> Central tolerance - they encounter antigens in the central lymphoid

organs when they are immature

Peripheral tolerance - they encounter antigens in the peripheral tissues in the

absence of other necessary signals




What is the major tolerance?


~~> Clonal deletion

The engagement of receptors on immature B cell or at cells lead to deletion




Which tolerance is more controlled?




Master01 | September, 2024/2025 | Latest update

, 2 | P a g e | © copyright 2024/2025 | Grade A+


~~> T cell tolerance

B cells can escape selection




Why is T cell tolerance more controlled?


~~> It can recognise self-MHC and autoantibodies but this means it will be

too good at recognition and can be killed




What are the 3 possible outcomes of random TCR gene rearrangement?


~~> Failure to recognise self-MHC (no survival signal)

Recognises self-MHC and peptide generates from self-antigen presented in

thymus (removed by negative selection as it binds too well)


Recognises self-MHC and any other peptide (expanded by positive selection)




Where is insulin expressed?


~~> Beta cells in the pancreas

It can't be expressed in the thymus




What is AIRE?


~~> autoimmune regulator protein

It is a transcription factor


Master01 | September, 2024/2025 | Latest update

, 3 | P a g e | © copyright 2024/2025 | Grade A+


Plays a role in tolerance induction




What does AIRE do?


~~> It allows the expression of normal tissue-specific antigens in the thymus

and hence deletion of T cell that recognise these antigens

This leads to autoimmune syndrome




What is the outcome of AIRE is present?


~~> The sucking can be expressed in our thymus and it will remove auto

reactive T cells - no T cells specific to insulin = diabetes




What is the outcome of AIRE is mutated?


~~> The insulin won't be expressed in the thymus; they will have lots of

autoreactive T cells causing immunity problems




What does random Ig gene rearrangement lead to?


~~> B cells expressing self-reactive BCR




What is receptor editing?




Master01 | September, 2024/2025 | Latest update

, 4 | P a g e | © copyright 2024/2025 | Grade A+


~~> B cells get a second chance to rearrange any self-reactive BCR

They have further light chain gene rearrangement so that there is a possibility

of expressing a receptor that's not self-reactive




What happens to the immature T cells that fail the positive selection?


~~> They undergo further rearrangements of the TCR alpha locus to

produce a different receptor




What genes rearrange the receptors?


~~> RAG genes




What are anergic lymphocytes?


~~> The unresponsive lymphocytes that recognise self-antigens




How are immature B cells formed?


~~> When receptors encounter antigens that is not multivalent, this forms

immature B cells which downregulate BCR




How do T cells become anergic?




Master01 | September, 2024/2025 | Latest update

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