Classical Flt3L-dependent dendritic cells control immunity to protein vaccine
1875 - 1891
The Journal of Experimental Medicine
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DCs are critical for initiating immunity. The current paradigm in vaccine biology is that DCs migrating from peripheral tissue and classical lymphoid-resident DCs (cDCs) cooperate in the draining LNs to initiate priming and proliferation of T cells. Here, we observe subcutaneous immunity is Fms-like tyrosine kinase 3 ligand (Flt3L) dependent. Flt3L is rapidly secreted after immunization; Flt3 deletion reduces T cell responses by 50%. Flt3L enhances global T cell and humoral immunity as well as both the numbers and antigen capture capacity of migratory DCs (migDCs) and LN-resident cDCs. Surprisingly, however, we find immunity is controlled by cDCs and actively tempered in vivo by migDCs. Deletion of Langerin+ DC or blockade of DC migration improves immunity. Consistent with an immune-regulatory role, transcriptomic analyses reveals different skin migDC subsets in both mouse and human cluster together, and share immune-suppressing gene expression and regulatory pathways. These data reveal that protective immunity to protein vaccines is controlled by Flt3L-dependent, LN-resident cDCs. Human vaccines are delivered through skin, commonly by the s.c. route, allowing access to a rich network of DCs in skin and skin-draining LNs (Romani et al., 2010). s.c. injected vaccine antigens reach LNs that drain the skin and epithelial surfaces by passive transport through lymphatics or by DC antigen capture followed by subsequent cell-bound trafficking to the LNs, where T cell priming occurs (Itano et al., 2003). Resident DCs and several distinct migratory DC subsets (migDCs) that traffic to LN from skin are present in LNs (Förster et al., 1999; Henri et al., 2010b). The current paradigm is that both LN-resident DCs and migDCs have access to s.c. delivered antigen, are requisite, and cooperate to induce immunity (Itano et al., 2003; Allenspach et al., 2008). Based on this paradigm, vaccinology efforts have focused heavily on delivery of antigens to skin-resident DCs. Flt3L is a DC hematopoietin that maintains DC numbers at set levels throughout adult life (Liu et al., 2007, 2009) and at sites relevant to vaccination, including the skin and skin-draining LN (Brasel et al., 1996; Maraskovsky et al., 1996). In healthy individuals, Flt3L is tightly regulated and at the limits of detection by ELISA; notably, it is 20-fold lower than CSF-1 or c-kit ligand (Shadle et al., 1989; Langley et al., 1993; Lyman and McKenna, 2003). Flt3L is secreted during acute infection, however, leading to DC-mediated support of NK function (Eidenschenk et al., 2010; Guermonprez, 2012). During s.c. immunization, the composition of DC subsets in the skin-draining LNs is transiently altered (Kastenmüller et al., 2011). It is unknown if Flt3L is secreted during immunization to regulate DC expansion acutely or if Flt3 signaling is required for productive immunity. Flt3L and its receptor (Flt3, FLK2) instruct progenitors along a DC developmental pathway regulating the mobilization of preDCs from the blood to give rise to IFN-α–producing PDC, CD8α+, and CD8αneg cDCs in lymphoid organs and tissue-resident DCs such as Langerin+CD103+ DCs in skin (Waskow et al., 2008). Lymphoid CD8α+ (Bozzacco et al., 2010) and tissue CD103+ DCs both cross-present antigens (the major pathway of tumor and viral antigen presentation), derive from preDCs (Ginhoux et al., 2009), and share Flt3L developmental dependence (Liu et al., 2009), with common regulation downstream of Flt3 by mTOR (Sathaliyawala et al., 2010). These findings suggest DC ontogeny may dictate function, one rationale for the use of hematopoetins to selectively drive DC development for clinical use. Flt3L is being reintroduced to the clinic to potentiate human vaccines. It is unclear if bias by Flt3L to cross-presenting DCs from skin and LN may be exploited for protein-based vaccine delivery. Also, Langerin+ CD103+ DCs, which are tissue-resident migDCs originating from skin, are specialized to cross-present viral antigens to T cells during cytolytic infection (Bedoui et al., 2009a). However, their role in immunization to viral antigens has not been established. We observe Flt3 is required for robust immunity to s.c. immunization and can enhance immunity. Surprisingly, we find that irrespective of Flt3L treatment, migDCs in the LN (including Langerin+ CD103+ cross-presenting DCs) are not required for CD4+ T cell effector function, despite having greater efficiency of s.c. protein capture in the LN than resident CD8α cDCs. Impairing DC migration from skin to the sdLN via knockout of the CCR7 receptor and deletion of migDC subsets including Langerin+CD103+ DCs enhanced, not diminished, immune priming. Rather, the immune response develops through CD11c+ ZBTB46-dependent cDCs. Transcriptomics in mouse and human reveal migDC subsets from skin relate most closely to each other and share gene signatures related to dampening of DC and T cell activation. Thus, we demonstrate that the immune response is controlled by cDCs in lymphoid tissue and that tissue microenvironment may confer immunosuppressive DC function in vivo.
AuthorsAnandasabapathy, N; Feder, R; Mollah, S; Tse, S-W; Longhi, MP; Mehandru, S; Matos, I; Cheong, C; Ruane, D; Brane, L; Teixeira, A; Dobrin, J; Mizenina, O; Park, CG; Meredith, M; Clausen, BE; Nussenzweig, MC; Steinman, RM
- Cardiovascular