[Frontiers in Bioscience 18, 422-440, January 1, 2013]

T lymphocyte trafficking: molecules and mechanisms

Hongmei Fu1, Amu Wang2, Claudio Mauro1, Federica Marelli-Berg1,2

1William Harvey Research Institute, Barts and The London School of Medicine and Dentistry, Queen Mary University of London, Charterhouse Square, London EC1M 6BQ, UK, 2Section of Immunobiology, Department of Medicine, Imperial College London, Hammersmith Hospital Campus, Du Cane Road, London W12 0NN, UK

TABLE OF CONTENTS

1. Abstract

2. Introduction - Lymphocyte recirculation and homing
3. T lymphocyte extravasation
4. Naïve T cell homing to the peripheral lymph nodes (PLN) and gut- associated lymphoid tissue
5. Memory T cell homing to non-lymphoid tissue
5.1. Memory T cell homing to the skin
5.2. Memory T cell homing to the small and large intestine
5.3. Memory T cell homing to the liver
5.4. Mechanisms of homing receptor acquisition
5.5. Antigen-driven T cell trafficking
5.6. Co-stimulatory molecules regulate T cell migration
5.7. PI3K-mediated control of T cell migration
6. Regulatory T cell trafficking
6.1. Naturally occurring regulatory T cells
6.2. Induced regulatory T cells
6.3. Tregs homing to secondary lymphoid organs
6.4. Tregs homing to nonlymphoid tissue
7. Concluding remarks
8. Acknowledgements
9. References

1. ABSTRACT

Coordinated migratory events are required for the development of effective and regulated immunity. Naïve T lymphocytes are programmed to recirculate predominantly in secondary lymphoid tissue by non-specific stimuli. In contrast, primed T cells must identify specific sites of antigen location in non-lymphoid tissue to exert targeted effector responses. Following priming, T cells acquire the ability to establish molecular interactions mediated by tissue-selective adhesion and chemokine receptors (homing receptors) that facilitate their access to specific organs. Recent studies have shown that an additional level of homing specificity is provided by the induction of T cell migration into the tissue by recognition of antigen displayed by the endothelium. In addition, co-stimulatory signals have been recently shown not only to regulate T cell activation and differentiation, but also to orchestrate the anatomy of the ensuing T cell response. Similarly, the characterization of migratory patterns by regulatory T cells has been the subject of many recent studies. Here, we provide an overview of key concepts, which have contribute to unraveling the complex anatomy of T cell immunity.