Step 3 of 7. Proteins are broken down within cells into short strings of amino acids called peptides

Proteins break down to peptides

Some peptides from each protein can bind to presentation platforms at the cell surface called MHC. This system ensures that there are peptides from every protein expressed inside a cell bound to MHC molecules on its surface. T cells are designed to scan these peptides in order to look for anomalies.

Usually, all these peptides will be 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.

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