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J Exp Med. 2018 Dec 3;215(12):2972-2983. doi: 10.1084/jem.20180344. Epub 2018 Nov 14.

The conduit system exports locally secreted IgM from lymph nodes.

Author information

1
Aix-Marseille Université, Centre National de la Recherche Scientifique, Institut National de la Santé et de la Recherche Médicale, Centre d'Immunologie de Marseille-Luminy, Marseille, France.
2
Division of Immunology, Transplantation and Infectious Diseases and Experimental Imaging Center, IRCCS San Raffaele Scientific Institute and Vita-Salute San Raffaele University, Milan, Italy.
3
Aix-Marseille Université, Centre National de la Recherche Scientifique, Institut de Biologie du Développement de Marseille, Marseille, France.
4
Aix-Marseille Université, Centre National de la Recherche Scientifique, Institut National de la Santé et de la Recherche Médicale, Centre d'Immunologie de Marseille-Luminy, Marseille, France bajenoff@ciml.univ-mrs.fr.

Abstract

Immunoglobulin M (IgM) is the first type of antibody produced during acute infections and thus provides an early line of specific defense against pathogens. Being produced in secondary lymphoid organs, IgM must rapidly be exported to the blood circulation. However, it is currently unknown how such large pentameric molecules are released from lymph nodes (LNs). Here, we show that upon immunization, IgM transiently gains access to the luminal side of the conduit system, a reticular infrastructure enabling fast delivery of tissue-derived soluble substances to the LN parenchyma. Using microinjections of purified IgM, we demonstrate that conduit-associated IgM is delivered by neither the afferent lymph nor the blood, but is locally conveyed by conduits. Exploiting in vivo models, we further demonstrate that conduit-associated IgM is locally and transiently produced by activated, antigen-specific B cells migrating in the T cell zone. Thus, our study reveals that the conduit system is coopted by B cells to rapidly export secreted IgM out of LNs.

PMID:
30429248
PMCID:
PMC6279403
[Available on 2019-06-03]
DOI:
10.1084/jem.20180344

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