Plasticity and heterogeneity of lymphoid organs What are the criteria to call a lymphoid organ primary, secondary or tertiary?

Plasticity and heterogeneity of lymphoid organs What are the criteria to call a lymphoid organ primary, secondary or tertiary?

Immunol Lett. 2007 Jul 24

Pabst R.
Department of Functional and Applied Anatomy, Medical School of Hannover, Carl-Neuberg-Str. 1, 30625 Hannover, Germany.

Lymphoid organs are generally classified in a hierarchy with primary lymphoid organs such as the thymus and bone marrow for the production of receptor specific T and B lymphocytes, respectively, independent of antigens.

In secondary lymphoid organs such as lymph nodes, spleen, and tonsils, the lymphocytes are expanded due to antigen exposure, producing memory T cells and effector B cells, resulting in plasma cells. Tertiary lymphoid tissues are often defined as aggregations of lymphoid cells in autoimmune diseases. It will be outlined that all these organs have a high plasticity and also the thymic medulla is included in the route of migrating mature T cells and the bone marrow, not only in the traffic of CD4(+) but also of CD8(+) lymphocytes.

The mucosa-associated lymphoid organs depend to a much larger extent on microbial antigen and are much more diverse than often described. The role of structural elements as well as blood and lymphatic vessels as an entry and exit site of lymphocytes will be outlined. Using a precise terminology, taking account of the plasticity of these organs at different ages and considering species differences will reduce misunderstandings among immunologists.

PMID: 17698207 [PubMed - as supplied by publisher]

Imaging of the lymphatic system: new horizons

Imaging of the lymphatic system: new horizons

Contrast Media Mol Imaging.

Barrett T, Choyke PL, Kobayashi H.
Molecular Imaging Program, National Cancer Institute, Building 10, Room 1B40, Bethesda, MD 20892-1088, USA.

Keywords:
Lymphatic imaging • sentinel node imaging • lymphangiography • contrast agent • lymphoscintigraphy

The lymphatic system is a complex network of lymph vessels, lymphatic organs and lymph nodes. Traditionally, imaging of the lymphatic system has been based on conventional imaging methods like computed tomography (CT) and magnetic resonance imaging (MRI), whereby enlargement of lymph nodes is considered the primary diagnostic criterion for disease. This is particularly true in oncology, where nodal enlargement can be indicative of nodal metastases or lymphoma. CT and MRI on their own are, however, anatomical imaging methods. Newer imaging methods such as positron emission tomography (PET), dynamic contrast-enhanced MRI (DCE-MRI) and color Doppler ultrasound (CDUS) provide a functional assessment of node status. None of these techniques is capable of detecting flow within the lymphatics and, thus, several intra-lymphatic imaging methods have been developed. Direct lymphangiography is an all-but-extinct method of visualizing the lymphatic drainage from an extremity using oil-based iodine contrast agents. More recently, interstitially injected intra-lymphatic imaging, such as lymphoscintigraphy, has been used for lymphedema assessment and sentinel node detection. Nevertheless, radionuclide-based imaging has the disadvantage of poor resolution. This has lead to the development of novel systemic and interstitial imaging techniques which are minimally invasive and have the potential to provide both structural and functional information; this is a particular advantage for cancer imaging, where anatomical depiction alone often provides insufficient information. At present the respective role each modality plays remains to be determined. Indeed, multi-modal imaging may be more appropriate for certain lymphatic disorders. The field of lymphatic imaging is ever evolving, and technological advances, combined with the development of new contrast agents, continue to improve diagnostic accuracy.

Wiley InterScience

Lymph node imaging: basic principles
Eur J Radiol.

Luciani A, Itti E, Rahmouni A, Meignan M, Clement O.
Service d'Imagerie Médicale, Hôpital Henri Mondor, 51 avenue du Maréchal de Lattre de Tassigny, 94010 Créteil cedex, France. alain.luciani@hmn.ap-hop-paris.fr

Keywords: Lymph node, Sentinel node, Magnetic resonance (MR), Positron emission tomography (PET), Computed tomography (CT

Lymph nodes are involved in a wide variety of diseases, particularly in cancer. In the latter, precise nodal staging is essential to guide therapeutic options and to determine prognosis. For long, imaging of the lymphatic system has been limited to lymph vessel,especially via the exclusive use of conventional lymphography, at the expense of invasive procedures and patient's discomfort. Three main technical advances, however, have recently completed the clinical armamentarium for lymph node imaging: first, the refinement of cross sectional imaging, i.e. CT and MRI, combined or not with dedicated contrast agents, has progressively replaced conventional lymphography in oncology situations; second, the development of intra-operative sentinel node mapping has profoundly modified the diagnostic and therapeutic procedures in several cancer situations, mostly melanoma and breast cancer; finally, the increased availability of functional imaging, especially through the use of FDG-PET, has greatly contributed to the accuracy improvement of nodal metastases identification. The aim of this review will thus be to briefly review the anatomy and physiology of the lymphatic systems and to overview the basic principles of up-to-date lymph node imaging.

Elsevier