Autoimmunity

What are memory T-cells?
After the process of T cell development where immature T cells gain the expression of their TCR and CD4 or CD8 co-receptor molecules, T cells undergo a process of thymic selection (also known as central tolerance) to ensure that those T cells expressing a non-functional or autoreactive TCR are deleted (negative selection) and only T cells expressing TCRs with low affinity for self-peptide/MHC survive and undergo further maturation (positive selection).
Central tolerance ensures that overtly autoreactive T cells are eliminated and that only mature thymocytes with low affinity for self-peptide/MHC populate the periphery.




Usually, all these peptides presented during thymic selection will derive from ‘self’ proteins and these should be ignored by the immune system. However, when a cell becomes cancerous or is infected by a germ it will express different proteins and display some different or ‘foreign’ peptides on its surface.

Autoimmunity is believed to occur when a T-cell that is selected and raised to fight infection then inadvertently recognises a peptide derived from a ‘self’ protein. The net result is that these T-cells then turn on our own tissues.
All autoimmune diseases are genetically linked to certain MHC molecules. MHC molecules are designed to present peptides to T-cells. We therefore believe that rogue T-cells are the root cause of all autoimmunity.