A phenomenon that occurs in the immune system of zebrafish has been witnessed for the first time by US researchers.

Using imaging techniques, a study at the University of Wisconsin–Madison (UW-Madison), saw how the adaptive immune system works by tracking the movement of fluorescently-labelled immune T cells in adult zebrafish, which had been genetically modified to remain transparent.

The adaptive immune system – comprised of different processes and immune cells to fight infections and toxins – is the body’s second line of defence after the innate immune system.

Unexpectedly, the researchers saw that the T cells circulated around the body in a highly organised way and repeating pattern, which had been previously theorised, but not directly observed.

Better understanding immunity can help in the development of vaccines, as well as shed light on certain disease processes and how immunity itself evolved.