MHC restrection

[sami a.r]

hey everyone,

i have two question and hope i will found the answers here

 

1. why are primed T cells restricted to be activated by peptides presented by the same MHC that was "used" to prime them?

 

2. Can we "train" a naive T cell to "see" a peptide presented by an allogeneic MHC and if yes How would you do the experiment to prove the hypothesis?

 

hope to recieve answers soon.

thanx you all

[Variola]

Hi

 

I am not totally sure what you mean, but I will give it a go.

 

T cells are restricted to MHC1 or MHC2as they both have other functions other than to recognise self/non self, there is a fine balance between the innate and acquired immune system. It is common to think of them as two different systems, in fact we are often taught them separately, but really the actions of one affect the actions of the other.

 

Your 2nd question I am not too sure what you mean. MHC class molecules structure vary a lot from person to person, hence we often have problems with organ donation and rejection.

For the T cell to be niave enough to recognise a different MHC it would have to be caught in its CD3/CD4+CD8 state before progression through the thymus. Assuming you could still induce the T cell to mature in the same way as it does in the thymus, but present a 'foreign' MHC mole to it, then in theory I suppose you could. But the maturation is heavily checkpointed, particularly at the CD4/CD8 expressing stage by the positive-negative restriction. You would have to ensure the cell got the signal to survive and the signal not to apoptose at both stages.

But assuming the cell wouldn't be fussy and happily induced into a CD4 or CD8, then the experiment would I suppose need to use a control sample of the same T cells 'trained' on their host MHC moles, as they would normally. Then to check for binding affinity..... well there are several methods you could use.... GFP conjugation plus fluorimetry perhaps? and sandwich ELISA too.... ?