How Do Immune Cells Recognise Whom To Attack?

Our immune systems have evolved over a long period of time, adapting in a never-ending arms-race against infections and abnormal cells. Part of this evolution has been in the way that immune cells recognise that something is wrong. The simpler cells of our immune system automatically recognise invading bacteria, but to detect viruses and cancer cells the most specialised cells of the immune system, the B and T lymphocytes have evolved ways to learn and recognise new targets.

Imagine this as a border sentry guard; “passport please”, asks the lymphocyte.

Each time a B or T-immune cell meets any other cell, the lymphocyte interrogates the identity of the cell by trying to match the proteins displayed on the outside of the cell. If the lymphocyte recognises the cell as “friend” then it is allowed to pass; if however the proteins on the surface of the cell are abnormal, then the lymphocyte identifies the cells as “foe”. The lymphocyte then raises the alarm, switching on its own attack systems but also sending off signals for help from the rest of the immune system.