• Mélanie Durand, Thomas Walter, Tiphène Pirnay, Thomas Naessens, Paul Gueguen, Christel Goudot, Sonia Lameiras, Qing Chang, Nafiseh Talaei, Olga Ornatsky, Tatiana Vassilevskaia, Sylvain Baulande, Sebastian Amigorena, and Elodie Segura.
• Institut Curie, Paris-Sciences-et-Lettres Research University, Institut National de la Santé et de la Recherche Médicale, U932, Paris, France.
• J. Exp. Med. 2019 Jul 1; 216 (7): 1561-1581.

AbstractCD4+ T follicular helper (Tfh) cells are essential for inducing efficient humoral responses. T helper polarization is classically orientated by dendritic cells (DCs), which are composed of several subpopulations with distinct functions. Whether human DC subsets display functional specialization for Tfh polarization remains unclear. Here we find that tonsil cDC2 and CD14+ macrophages are the best inducers of Tfh polarization. This ability is intrinsic to the cDC2 lineage but tissue dependent for macrophages. We further show that human Tfh cells comprise two effector states producing either IL-21 or CXCL13. Distinct mechanisms drive the production of Tfh effector molecules, involving IL-12p70 for IL-21 and activin A and TGFβ for CXCL13. Finally, using imaging mass cytometry, we find that tonsil CD14+ macrophages localize in situ in the B cell follicles, where they can interact with Tfh cells. Our results indicate that human lymphoid organ cDC2 and macrophages play complementary roles in the induction of Tfh responses.© 2019 Durand et al.

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