Immune memory
Immune memory was first documented in ancient Greece by the historian Thucydides who noted that "the same man was never attacked twice" when he described the plague of Athens in 430 BC. Remarkably, these observations were made more than 2,000 years before we knew about the immune system and that microbial pathogens cause disease. Now, it is well established that immune memory is an integral part of adaptive immunity to ensure long-lasting protection against previously encountered pathogens. Traditionally, immune memory has been associated with T cells and B cells, which mount a more rapid and robust response upon re-encounter with antigens. Increasing evidence indicates that innate immune cells can also 'remember' certain previously encountered immune stimuli.
The articles in this Focus issue describe our progress in understanding immune memory in different immune cell types, including CD8+ T cells, regulatory T cells, tissue-resident memory T cells and natural killer cells. Finally, in a Viewpoint article, five leaders in the field discuss their definition of immune memory, their views on memory responses by innate immune cells and consider the key questions that remain for the field.
