Germs in our body leave a trail of clues – fragments of their DNA – that are picked up by dendritic cells, the detectives of our immune system. These sleuths alert an army of other cells that hunt down and destroy the invaders. Scientists investigating how dendritic cells work have found that a protein called DEC-205 performs a crucial step. It sits on the cell surface and latches onto chunks of alien DNA, dragging them across the dendritic cell wall to special receptors inside. Here, we see dendritic cells from two mice. In the cell on the left, some DNA fragments are at the receptor site (the dots stained yellow) and others (shown in red) are elsewhere inside the cell, possibly in transit. But in the cell on the right, from a mouse genetically engineered to lack DEC-205, there are no fragments.
Written by Mick Warwicker
BPoD stands for Biomedical Picture of the Day. Managed by the MRC London Institute of Medical Sciences the website aims to engage everyone, young and old, in the wonders of biomedicine. Images are kindly provided for inclusion on this website through the generosity of scientists across the globe.