The evolving biology of T cell memory: A dynamic continuum of function and persistence.

Immunological memory underpins long-term protection and vaccination. Although early work established the durability and recall capacity of memory T cells, understanding of CD8 T cell memory generation, maintenance, and plasticity has advanced substantially over recent decades. Initial models viewed memory as an outcome of peak effector responses and were defined mainly by persistence. Successive waves of technological innovation, from MHC tetramers and genetic lineage-tracing approaches to single-cell and epigenomic profiling and modern high-throughput gene-perturbation screens, have reshaped this view. These approaches reveal memory as a dynamic continuum of cellular states that is actively maintained, tissue-adapted, and epigenetically programmed. CD8 T cell memory is now understood as a flexible and regulated fate rather than a static end point. In this Review, we outline the historical development of the field, highlight how emerging technologies have refined core concepts, and present a modern framework in which memory is an actively enforced yet adaptable property of the CD8 T cell lineage.