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Trends Immunol. 2010 Apr;31(4):144-53. doi: 10.1016/ Epub 2010 Feb 22.

B-cells need a proper house, whereas T-cells are happy in a cave: the dependence of lymphocytes on secondary lymphoid tissues during evolution.

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  • 1Division of Neuroimmunology, Inst. Exp. Immunology, Department of Pathology, University Hospital of Zurich, 8057 Zurich, Switzerland.


A fundamental tenet of immunology is that adaptive immune responses are initiated in secondary lymphoid tissues. This dogma has been challenged by several recent reports. We discuss how successful T cell-mediated immunity can be initiated outside of such dedicated structures, whereas they are required for adaptive humoral immunity. This resembles an ancient immune pathway in the oldest cold-blooded vertebrates, which lack lymph nodes and sophisticated B-cell responses including optimal affinity maturation. The T-cell, however, has retained the capacity to recognize antigen in a lymph node-free environment. Besides bone marrow and lung, the liver is one organ that can potentially serve as a surrogate lymphoid organ and could represent a remnant from the time before lymph nodes developed.

Copyright 2010 Elsevier Ltd. All rights reserved.

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