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
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