Tuesday, 29 May 2012

Education: How is a T cell stimulated

We have talked about the major histocompatibility complex (MHC) and how this is gives us our identities and allows use to distinguish ourselves from invaders into the body.
The  T cell has a molecule that allows it to see its target. This is called the T cell receptor. There are many variants and this allows them to recognise alot (a billion billion) of targets

These come together so the T cell receptor recognises a linear sequence of amino acids and the MHC (=HLA).
There are twenty different amino acids that protiens are made from and T cells recognise 9-13 amino acids in a sequence. Some of the amino acids bind to the HLA and others bind to the T cell receptor. It is possible that a T cell that recognises a virus or bacteria could also react with a brain protein.
Each circle (above) is an amino acid the different colours represent different amino acids, white ones mean their identity are not important. Responses to Bacteria/virus 2 could cross-react with the brain protien. This is known as Molecular mimicry and is defined as the theoretical possibility that sequence similarities between foreign and self-peptides are sufficient to result in the cross-activation of autoreactive  (autoimmune) T or B cells by pathogen-derived peptides.

1 comment:

  1. I finally understood molecular mimicry - thank you!

    ReplyDelete

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