Fate mapping reveals origin and dynamics of lymph node follicular dendritic cells.
Bottom Line: In vitro and ex vivo methods, therefore, allow only limited understanding of the genuine immunobiology of FDCs in their native habitat.Herein, we used various multicolor fate mapping systems to investigate the ontogeny and dynamics of lymph node (LN) FDCs in situ.We further demonstrate that during an immune response, FDCs accumulate in germinal centers and that neither the recruitment of circulating progenitors nor the division of local mature FDCs significantly contributes to this accumulation.
Affiliation: Centre d'Immunologie de Marseille-Luminy (CIML), Aix-Marseille Université, UM2 Marseille, France Institut National de la Santé et de la Recherche Médicale (INSERM), UMR_S 1104 Marseille, France Centre National de la Recherche Scientifique (CNRS), UMR7280 Marseille, France Aix-Marseille Univ (AMU), F-13284 Marseille, France.Show MeSH
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Mentions: One of the key functions of FDCs is the organization of GC structures devoted to the development and maturation of B cell responses (MacLennan, 1994; Allen et al., 2007; Wang et al., 2011; Victora and Nussenzweig, 2012). GCs contain enlarged FDC networks of unknown origin (Allen et al., 2004, 2007; Allen and Cyster, 2008). A previous report indicated that during carcinogenesis, at least 20% of carcinoma-associated fibroblasts originate from BM-derived mesenchymal stem cells (Quante et al., 2011). We thus sought to determine whether FDCs in inflamed follicles also arose from the recruitment of BM-derived stromal cells or derived from the proliferation of resident FDCs. We first addressed the contribution of blood-derived FDC precursors. To this aim, we took advantage of Wnt-1Cre Ubow mice in which cervical and auricular LNs display CFP+ and YFP+ FDCs at steady-state (Fig. 1 B). We injected an emulsion of OVA in CFA in the ears and rear footpads of these mice and analyzed the FDC networks of their auricular and popliteal LNs 3 wk later. As expected, confocal microscopy indicated that the FDC networks of inflamed auricular LNs contained CFP+ and YFP+ FDCs (Fig. 2 A, left). However, none of the inflamed popliteal LNs displayed CFP+ or YFP+ FDCs, ruling out the possibility that circulating neural crest–derived mesenchymal precursors migrated into reactive LNs and generated FDCs (Fig. 2 A, right). To exclude the implication of other circulating mesenchymal derived progenitors, we set up parabiotic pairs of mice consisting of CD21Cre Ubow+/− µMT mice surgically attached to WT counterparts (Kitamura et al., 1991; Waskow, 2010; Fig. 2 B). In such parabionts, both mice share their blood circulation and thus a common probability to recruit a putative circulating FDC precursor. If such precursor arises from the CD21Cre Ubow+/− µMT partner, it should generate CFP+ or YFP+ mature CD21/35+ FDCs upon its engraftment in the reactive LNs of the WT mouse. 3 mo after the surgery, the WT partners (all displaying full chimerism) were injected with CFA/OVA in their rear footpads. 3 wk later, their inflamed popliteal LNs were analyzed by confocal microscopy for the presence of CFP+ or YFP+ CD21/35+ FDCs. Analysis indicated that CFP+ or YFP+ CD21/35+ FDCs were absent in the inflamed follicles of the WT parabionts (Fig. 2 B) while all the follicles of CD21Cre Ubow+/− µMT partners displayed YFP or CFP FDC networks as a result of WT B cell seeding. Altogether, our results rule out the possibility that reactive FDC networks incorporate putative blood-derived FDCs.
Affiliation: Centre d'Immunologie de Marseille-Luminy (CIML), Aix-Marseille Université, UM2 Marseille, France Institut National de la Santé et de la Recherche Médicale (INSERM), UMR_S 1104 Marseille, France Centre National de la Recherche Scientifique (CNRS), UMR7280 Marseille, France Aix-Marseille Univ (AMU), F-13284 Marseille, France.