Memory versus naive T‐cell migration

Our established understanding of lymphocyte migration suggests that naive and memory T cells travel throughout the body via divergent pathways; naive T cells circulate between blood and lymph whereas memory T cells additionally migrate through non‐lymphoid organs. Evidence is now gradually emerging which suggests such disparate pathways between naive and memory T cells may not strictly be true, and that naive T cells gain access to the non‐lymphoid environment in numbers approaching that of memory T cells. We discuss here the evidence for naive T‐cell traffic into the non‐lymphoid environment, compare and contrast this movement with what is known of memory T cells, and finally discuss the functional importance of why naive T cells might access the parenchymal tissues.