IRF4 transcription factor-dependent CD11b+ dendritic cells in human and mouse control mucosal IL-17 cytokine responses.

Mouse and human dendritic cells (DCs) are composed of functionally specialized subsets, but precise interspecies correlation is currently incomplete. Here, we showed that murine lung and gut lamina propria CD11b+ DC populations were comprised of two subsets: FLT3- and IRF4-dependent CD24(+)CD64(-) DCs and contaminating CSF-1R-dependent CD24(-)CD64(+) macrophages. Functionally, loss of CD24(+)CD11b(+) DCs abrogated CD4+ T cell-mediated interleukin-17 (IL-17) production in steady state and after Aspergillus fumigatus challenge. Human CD1c+ DCs, the equivalent of murine CD24(+)CD11b(+) DCs, also expressed IRF4, secreted IL-23, and promoted T helper 17 cell responses. Our data revealed heterogeneity in the mouse CD11b+ DC compartment and identifed mucosal tissues IRF4-expressing DCs specialized in instructing IL-17 responses in both mouse and human. The demonstration of mouse and human DC subsets specialized in driving IL-17 responses highlights the conservation of key immune functions across species and will facilitate the translation of mouse in vivo findings to advance DC-based clinical therapies

CD8+ T Cells and IFN-γ Mediate the Time-Dependent Accumulation of Infected Red Blood Cells in Deep Organs during Experimental Cerebral Malaria

Background: Infection with Plasmodium berghei ANKA (PbA) in susceptible mice induces a syndrome called experimental cerebral malaria (ECM) with severe pathologies occurring in various mouse organs. Immune mediators such as T cells or cytokines have been implicated in the pathogenesis of ECM. Red blood cells infected with PbA parasites have been shown to accumulate in the brain and other tissues during infection. This accumulation is thought to be involved in PbA–induced pathologies, which mechanisms are poorly understood. Methods and Findings: Using transgenic PbA parasites expressing the luciferase protein, we have assessed by real-time in vivo imaging the dynamic and temporal contribution of different immune factors in infected red blood cell (IRBC) accumulation and distribution in different organs during PbA infection. Using deficient mice or depleting antibodies, we observed that CD8 + T cells and IFN-c drive the rapid increase in total parasite biomass and accumulation of IRBC in the brain and in different organs 6–12 days post-infection, at a time when mice develop ECM. Other cells types like CD4 + T cells, monocytes or neutrophils or cytokines such as IL-12 and TNF-a did not influence the early increase of total parasite biomass and IRBC accumulation in different organs. Conclusions: CD8 + T cells and IFN-c are the major immune mediators controlling the time-dependent accumulation of P. berghei-infected red blood cells in tissues

Protection Against Graft-Versus-Host Disease and Retention of Graft-Versus-Tumor Effect after Allogeneic BMT in Mice Conditioned with TLI and Anti-Thymocyte Serum

Abstract In a completely MHC-mismatched model of bone marrow transplantation [C57BL/6 (H-2b) donors into BALB/c (H-2d) hosts], we have developed a technique of non-myeloablative host conditioning using fractionated total lymphoid irradiation (TLI) and and anti-thymocyte serum (ATS) that prevents lethal graft-versus-host disease (GVHD). We have previously reported that this GVHD prevention is dependent on the secretion of IL-4 and on host regulatory NKT cells. In the current study, we assessed the graft-versus-tumor (GVT) effect of BMT to determine whether the GVT effect remains intact in this non-myeloablative conditioning model. Male BALB/c mice were given fractionated TLI (17 doses of 240 cGy each), 3 doses of ATS, and subsequently received intravenous infusion of 50 x 106 bone marrow and 60x 106 splenocytes from C57BL/6 donors, with and without the BCL1 B-cell lymphoma. Animals were observed for minimum of 100 days, and underwent autopsy at death to assess for sub-clinical evidence of GVHD or tumor infiltration. TLI/ATS-conditioned mice achieved a high percentage of donor chimerism, in the range of 50–100% in all lineages. TLI/ATS-conditioned hosts uniformly survived without signs of GVHD beyond day +100. By contrast, hosts conditioned with a single dose of 800cGy total body irradiation (TBI) died of acute GVHD (severe diarrhea, hunched back, weight loss) by day +21. When TBI/ATS or TBI-treated mice receive bone marrow, splenocytes, and BCL1 lymphoma, all hosts died with signs of acute GVHD by day +28. TLI/ATS-conditioned hosts receiving marrow, splenocytes and tumor cells showed no evidence of disease progression by day +100 and either cleared tumor idiotype completely or had persistence of low-intensity staining for tumor idiotype (tumor dormancy). TLI/ATS-conditioned hosts given BCL1 tumor cells without allogeneic BMT all succumbed to tumor. TLI/ATS hosts receiving bone marrow plus BCL1 without splenocytes all died by day +108 with high circulating BCL1 tumor burden and no clinical evidence of GVHD. The data indicate that peripheral donor T cells are necessary to maintain a robust graft-versus-tumor effect after TLI/ATS conditioning, and that complete donor chimerism is not a requirement for tumor eradication. In conclusion, using the TLI/ATS non-myeloablative conditioning regimen, it is possible to maintain a clinically significant graft-versus-tumor effect without inducing GVHD despite a high dose of infused donor peripheral T cells

Donor CD8+ T Cells Facilitate Graft-Versus-Tumor Effect Via Alloantigen Rather Than Tumor-Specific Antigen Recognition Following Murine Myeloablative BMT

Abstract Previous data from our group and others has shown that donor CD8+ Tcells mediate graft-versus-tumor (GVT) function in murine myeloablative bone marrow transplantation (BMT) via Perforin/Fas ligand-dependent mechanisms. However, there has to date been no analysis of the mechanism of tumor recognition (i.e allo- versus tumor-specific antigen recognition) by donor CD8+ T cells following myeloablative MHC-mismatched BMT. In order to test the hypothesis that donor CD8 T-cells require allo-antigen recognition to maintain graft-versus-tumor effect, we developed stable full chimeras by transplanting T-cell depleted bone marrow (TCD BM) from C57BL/6 (H-2b) donor mice into myeloablated BALB/c (H-2d) hosts given 800 cGy total body irradiation (TBI) and evaluated the in vivo ability of CD8+ TCR+ splenocytes from these donors to kill the BCL1 tumor (a BALB/c-derived B-cell lymphoma carrying a detectable tumor-specific idiotype which can be monitored via peripheral blood flow cytometric analysis). These chimeras showed complete donor chimerism in myeloid, B- and T-lymphocytic lineages by day +100 following transplantation, and splenocytes from these chimeras exhibited tolerance to host-type but not third-party alloantigens. BALB/c hosts were given 800 cGy TBI on day -1, followed on day 0 by intravenous administration of 500 BCL1 tumor cells and infusion of 0.3x 106 CD8+ T cells of C57 origin (H-2b+) sorted by flow cytometric analysis from the either spleens of the chimeric mice or from the spleens of untreated wild-type C57BL/6 mice. All hosts were given 5 x 106 T cell-depleted wild-type C57 bone marrow cells. All mice were observed for clinical signs of graft-versus-host disease (GVHD) and mortality through day +100. Autopsy was performed at death to assess for sub-clinical target organ involvement with GVHD or tumor. Donor chimerism and BCL1 status was assessed at day +28 and day +100 by 3-color flow cytometric analysis for donor-specific MHC versus T-, B- and myeloid lineage markers as well as tumor-specific idiotype in the peripheral blood (or in the spleen at time of death for animals dying prior to day +100). All animals receiving BCL1 tumor cells and sorted CD8+T cells from wild-type untreated C57 donors cleared tumor idiotype but succumbed to GVHD. All animals receiving tumor cells and sorted chimeric C57 CD8+ T cells remained free of clinical or pathologic evidence of GVHD, but died with tumor progression. Control myeloablated animals given C57 TCD BM alone with BCL1 tumor cells all succumbed to tumor, whereas those receiving C57 whole bone marrow with tumor demonstrated tumor survival without GVHD. The data indicate that chimeric donor peripheral CD8+ T cells, which lose their capacity to induce lethal GVHD in BALB/c hosts, also lose the capacity to eradicate BALB/c-type lymphoma cells. We conclude that CD8+ T cell-induced GVT effect in this model is dependent upon alloantigen rather than tumor-specific antigen recognition

Host NKT Cells Can Prevent Graft-versus-Host Disease and Permit Graft Antitumor Activity after Bone Marrow Transplantation

Allogeneic bone marrow transplantation is a curative treatment for leukemia and lymphoma, but graft-vs-host disease (GVHD) remains a major complication. Using a GVHD protective nonmyeloablative conditioning regimen of total lymphoid irradiation and antithymocyte serum (TLI/ATS) in mice that has been recently adapted to clinical studies, we show that regulatory host NKT cells prevent the expansion and tissue inflammation induced by donor T cells, but allow retention of the killing activity of donor T cells against the BCL(1) B cell lymphoma. Whereas wild-type hosts given transplants from wild-type donors were protected against progressive tumor growth and lethal GVHD, NKT cell-deficient CD1d(−/−) and Jα-18(−/−) host mice given wild-type transplants cleared the tumor cells but died of GVHD. In contrast, wild-type hosts given transplants from CD8(−/−) or perforin(−/−) donors had progressive tumor growth without GVHD. Injection of host-type NKT cells into Jα-18(−/−) host mice conditioned with TLI/ATS markedly reduced the early expansion and colon injury induced by donor T cells. In conclusion, after TLI/ATS host conditioning and allogeneic bone marrow transplantation, host NKT cells can separate the proinflammatory and tumor cytolytic functions of donor T cells

The earliest intrathymic precursors of CD8α(+) thymic dendritic cells correspond to myeloid-type double-negative 1c cells.

International audienceThe dendritic cells (DCs) present in lymphoid and non-lymphoid organs are generated from progenitors with myeloid-restricted potential. However, in the thymus a major subset of DCs expressing CD8α and langerin (CD207) appears to stand apart from all other DCs in that it is thought to derive from progenitors with lymphoid potential. Using mice expressing a fluorescent reporter and a diphtheria toxin receptor under the control of the cd207 gene, we demonstrated that CD207(+) CD8α(+) thymic DCs do not share a common origin with T cells but originate from intrathymic precursors that express markers that are normally present on all (CD11c(+) and MHCII molecules) or on some (CD207, CD135, CD8α, CX3CR1) DC subsets. Those intrathymic myeloid-type precursors correspond to CD44(+) CD25(-) double-negative 1c (DN1c) cells and are continuously renewed from bone marrow-derived canonical DC precursors. In conclusion, our results demonstrate that the earliest intrathymic precursors of CD8α(+) thymic DCs correspond to myeloid-type DN1c cells and support the view that under physiological conditions myeloid-restricted progenitors generate the whole constellation of DCs present in the body including the thymus

Tissue-resident macrophages self-maintain locally throughout adult life with minimal contribution from circulating monocytes

Despite accumulating evidence suggesting local self-maintenance of tissue macrophages in the steady state, the dogma remains that tissue macrophages derive from monocytes. Using parabiosis and fate-mapping approaches, we confirmed that monocytes do not show significant contribution to tissue macrophages in the steady state. Similarly, we found that after depletion of lung macrophages, the majority of repopulation occurred by stochastic cellular proliferation in situ in a macrophage colony-stimulating factor (M-Csf)- and granulocyte macrophage (GM)-CSF-dependent manner but independently of interleukin-4. We also found that after bone marrow transplantation, host macrophages retained the capacity to expand when the development of donor macrophages was compromised. Expansion of host macrophages was functional and prevented the development of alveolar proteinosis in mice transplanted with GM-Csf-receptor-deficient progenitors. Collectively, these results indicate that tissue-resident macrophages and circulating monocytes should be classified as mononuclear phagocyte lineages that are independently maintained in the steady state

Human tissues contain CD141hi cross-presenting Dendritic cells with functional homology to mouse CD103+ nonlymphoid Dendritic cells

SummaryDendritic cell (DC)-mediated cross-presentation of exogenous antigens acquired in the periphery is critical for the initiation of CD8+ T cell responses. Several DC subsets are described in human tissues but migratory cross-presenting DCs have not been isolated, despite their potential importance in immunity to pathogens, vaccines, and tumors and tolerance to self. Here, we identified a CD141hi DC present in human interstitial dermis, liver, and lung that was distinct from the majority of CD1c+ and CD14+ tissue DCs and superior at cross-presenting soluble antigens. Cutaneous CD141hi DCs were closely related to blood CD141+ DCs, and migratory counterparts were found among skin-draining lymph node DCs. Comparative transcriptomic analysis with mouse showed tissue DC subsets to be conserved between species and permitted close alignment of human and mouse DC subsets. These studies inform the rational design of targeted immunotherapies and facilitate translation of mouse functional DC biology to the human setting