¹School of Clinical Veterinary Science, University of Bristol, Langford, Bristol, UK

Correspondence: Dr S Cose, School of Clinical Veterinary Science, University of Bristol, Langford House, Langford, Bristol BS40 5DU, UK. E-mail: s.cose@bristol.ac.uk

Received 28 June 2007; Revised 5 October 2007; Accepted 9 October 2007; Published online 13 November 2007.

Abstract

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.