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Nature Reviews Immunology 2, 60–65 (1 January 2002) | doi:10.1038/nri706

A role for antigen in the maintenance of immunological memory

David Gray

The immune system has a memory that it exhibits in the enhanced and augmented responses the second time it meets an antigen. The memory is the result of a number of changes to the system brought about during the primary response. The most important of these changes is the formation of an expanded pool of antigen-specific memory cells. One of the enduring questions in immunology is how these memory cells are maintained for such long periods.