Distributed memory

The distribution and quantity of CD4⁺ or CD8⁺ memory T cells throughout the body are largely unknown. In Blood, Baltimore and colleagues use a combination of whole-body imaging and flow cytometry to determine the number of memory T cells in various compartments. After adoptive transfer, CD4⁺ or CD8⁺ cells initially assume a similar distribution pattern (gut and lung), but during the expansion and contraction phases, when memory cells develop, they coalesce into distinct compartments. Specifically, CD8⁺ T cells show tropism for peripheral lymph nodes, whereas CD4⁺ T cells accumulate in the gut. This distribution pattern continues long term (>8 weeks) and is by and large the same whether cells are effector memory or central memory cells or are in any of the helper T cell subsets (T_H1, T_H2 or T_H17). These distributions are a direct consequence of the relative expression of chemokines and integrin receptors on the cells and their trophic cytokine requirements.

Blood 118, 3039–3050 (2011)