Immune memory is achieved by epigenetic and topological rearrangements of DNA in immune cells, research suggests

The immune system is one of the most complex parts of our body. It keeps us healthy by getting rid of parasites, viruses or bacteria, and by destroying damaged or cancer cells. One of its most intriguing abilities is its memory: upon first contact with a foreign component (called antigens) our adaptive immune system takes around two weeks to respond, but responses afterwards are much faster, as if the cells remembered the antigen. But how is this memory attained?