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Mannose receptor high, M2 dermal macrophages mediate nonhealing Leishmania major infection in a Th1 immune environment.

ABSTRACT: The origin and functional specialization of dermal macrophages in cutaneous infections have been little studied. In this paper, we show that a strain of Leishmania major (L. major Seidman [LmSd]) that produces nonhealing cutaneous lesions in conventionally resistant C57BL/6 mice was more efficiently taken up by M2-polarized bone marrow (BM)-derived macrophages (BMDMs) in vitro and by mannose receptor (MR)hi dermal macrophages in vivo compared with a healing strain (L. major Friedlin V1). Both in steady and in T helper type 1 (Th1) cell-driven inflammatory states, the MRhi dermal macrophages showed M2 characteristics. The dermal macrophages were radio resistant and not replaced by monocytes or adult BM-derived cells during infection, but were locally maintained by IL-4 and IL-10. Notably, the favored infection of M2 BMDMs by LmSd in vitro was MR dependent, and genetic deletion of MR or selective depletion of MRhi dermal macrophages by anti-CSF-1 receptor antibody reversed the nonhealing phenotype. We conclude that embryonic-derived, MRhi dermal macrophages are permissive for parasite growth even in a strong Th1-immune environment, and the preferential infection of these cells plays a crucial role in the severity of cutaneous disease.

SUBMITTER: Lee SH

PROVIDER: S-EPMC5748861 | biostudies-literature | 2018 Jan

REPOSITORIES: biostudies-literature

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Mannose receptor high, M2 dermal macrophages mediate nonhealing Leishmania major infection in a Th1 immune environment.

Lee Sang Hun SH Charmoy Melanie M Romano Audrey A Paun Andrea A Chaves Mariana M MM Cope Frederick O FO Ralph David A DA Sacks David L DL

The Journal of experimental medicine 20171215 1

The origin and functional specialization of dermal macrophages in cutaneous infections have been little studied. In this paper, we show that a strain of Leishmania major (L. major Seidman [LmSd]) that produces nonhealing cutaneous lesions in conventionally resistant C57BL/6 mice was more efficiently taken up by M2-polarized bone marrow (BM)-derived macrophages (BMDMs) in vitro and by mannose receptor (MR)hi dermal macrophages in vivo compared with a healing strain (L. ...[more]

PMID: 29247046

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Project description:Macrophages host Leishmania major infection, which causes cutaneous Leishmaniasis in humans. In the murine model, resistance to infection depends on the host immunity mediated by CD4 T-cell cytokines and macrophages. In association to other stimuli, the Th1 cytokine IFN-? induces NO-mediated microbial killing by M1/classically-activated macrophages. By contrast, the Th2 cytokine IL-4 promotes M2/alternatively activated macrophages, which express arginase-1 and shelter infection. Other cytokines, such as RANKL, might also participate in the crosstalk between T cells and macrophages to restrict parasite infection. RANKL and its receptor RANK are known to play an essential role in bone remodeling, by inducing osteoclatogenesis. It has also been shown that RANKL stimulates antigen-presenting cells, such as DCs and macrophages, to enhance T cell responses. Here we investigated how RANKL directly modulates the effector macrophage phenotypes and immunity to L. major parasites. We found that inflammatory peritoneal macrophages from B6 mice express RANK and M2 features, such as CD301 (MGL) and CD206 (mannose receptor). Nonetheless, treatment with RANKL or IFN-? induced macrophage differentiation into more mature F40/80hi macrophages able to produce IL-12 and TNF-?. In parallel, macrophages treated with RANKL, IFN-?, or RANKL along with IFN-? progressively downregulated the expression of the M2 hallmarks MGL, arginase-1, and CCL17. Moreover, a synergism between IFN-? and RANKL enhanced inducible NO synthase (iNOS) expression and NO production by macrophages. These results are consistent with the idea that RANKL helps IFN-? to induce a M2-like to M1 phenotype shift. Accordingly, concomitant treatment with RANKL and IFN-? promoted macrophage-mediated immunity to L. major, by inducing NO and ROS-dependent parasite killing. Furthermore, by cooperating with IFN-?, endogenous RANKL engages CD4 T-cell help toward L. major-infected macrophages to upregulate M1 and Th1 cytokine responses. Therefore, RANKL, in combination with IFN-?, is a potential local therapeutic tool to improve immune responses in Leishmaniasis, by skewing M2-like into effector M1 macrophages.

Project description:Protozoan parasites of the genus Leishmania alternate between flagellated, elongated extracellular promastigotes found in insect vectors, and round-shaped amastigotes enclosed in phagolysosome-like Parasitophorous Vacuoles (PVs) of infected mammalian host cells. Leishmania amazonensis amastigotes occupy large PVs which may contain many parasites; in contrast, single amastigotes of Leishmania major lodge in small, tight PVs, which undergo fission as parasites divide. To determine if PVs of these Leishmania species can fuse with each other, mouse macrophages in culture were infected with non-fluorescent L. amazonensis amastigotes and, 48 h later, superinfected with fluorescent L. major amastigotes or promastigotes. Fusion was investigated by time-lapse image acquisition of living cells and inferred from the colocalization of parasites of the two species in the same PVs. Survival, multiplication and differentiation of parasites that did or did not share the same vacuoles were also investigated. Fusion of PVs containing L. amazonensis and L. major amastigotes was not found. However, PVs containing L. major promastigotes did fuse with pre-established L. amazonensis PVs. In these chimeric vacuoles, L. major promastigotes remained motile and multiplied, but did not differentiate into amastigotes. In contrast, in doubly infected cells, within their own, unfused PVs metacyclic-enriched L. major promastigotes, but not log phase promastigotes--which were destroyed--differentiated into proliferating amastigotes. The results indicate that PVs, presumably customized by L. major amastigotes or promastigotes, differ in their ability to fuse with L. amazonensis PVs. Additionally, a species-specific PV was required for L. major destruction or differentiation--a requirement for which mechanisms remain unknown. The observations reported in this paper should be useful in further studies of the interactions between PVs to different species of Leishmania parasites, and of the mechanisms involved in the recognition and fusion of PVs.

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Mannose receptor high, M2 dermal macrophages mediate nonhealing Leishmania major infection in a Th1 immune environment.

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Mannose receptor high, M2 dermal macrophages mediate nonhealing <i>Leishmania major</i> infection in a Th1 immune environment.

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