T cells orchestrate pathogen-specific adaptive immune responses by identifying peptides
derived from pathogenic proteins that are displayed on the surface of infected cells. Host
cells also display peptide fragments from the host's own proteins. Incorrectly identifying
peptides derived from the body's own proteome as pathogenic can result in autoimmune
disease. To minimize autoreactivity, immature T cells that respond to self-peptides are
deleted in the thymus by a process called negative selection. However, negative selection is …

T-cells are the central players in the drama. They are a type of white blood cell that matures
in the thymus 2 where the first part of the story plays out. Each T-cell comes with a receptor
that can potentially bind to a short peptide string. A mature T-cell, which leaves the thymus
and circulates in the blood, uses its T-Cell Receptor (TCR) to patrol for foreign proteins. In
particular, infected cells put up a type of distress signal by putting fragments of the foreign
proteins on their surface where they can interact with the TCR. Should the TCR bind strongly …