It has been shown recently that neutrophils are able to produce IL-22 and IL-17, which differentially regulate the pathogenesis of inflammatory bowel disease (IBD). However, it is still largely unknown how the neutrophil production of IL-22 and IL-17 is regulated, and their role in the pathogenesis of IBD. In this study, we found that IL-23 promoted neutrophil production of IL-17 and IL-22. IL-23 stimulated the neutrophil expression of IL-23 receptor as well as rorc and ahr. RORγt and AhR differentially regulated IL-23 induction of neutrophil IL-17 and IL-22. Additionally, IL-23 induced the activation of mTOR in neutrophils. Blockade of mTOR pathway inhibited IL-23-induced expression of rorc and ahr as well as IL-17 and IL-22 production. By utilizing a microbiota antigen specific T-cell mediated colitis model, we demonstrated that depletion of neutrophils, as well as blockade of IL-22, resulted in a significant increase in the severity of colitis, thereby indicating a protective role of neutrophils and IL-22 in chronic colitis. Collectively, our data revealed that neutrophils negatively regulate microbiota antigen specific T cell induction of colitis, and IL-23 induces neutrophil production of IL-22 and IL-17 through induction of rorc and ahr, which is mediated by mTOR pathway.

Neutrophils are the first cells to infiltrate to the site of Leishmania promastigote infection, and these cells help to reduce parasite burden shortly after infection is initiated. Several clinical reports indicate that neutrophil recruitment is sustained over the course of leishmaniasis, and amastigote-laden neutrophils have been isolated from chronically infected patients and experimentally infected animals. The goal of this study was to compare how thioglycolate-elicited murine neutrophils respond to L. amazonensis metacyclic promastigotes and amastigotes derived from axenic cultures or from the lesions of infected mice. Neutrophils efficiently internalized both amastigote and promastigote forms of the parasite, and phagocytosis was enhanced in lipopolysaccharide (LPS)-activated neutrophils or when parasites were opsonized in serum from infected mice. Parasite uptake resulted in neutrophil activation, oxidative burst, and accelerated neutrophil death. While promastigotes triggered the release of tumor necrosis factor alpha (TNF-␣), uptake of amastigotes preferentially resulted in the secretion of interleukin-10 (IL-10) from neutrophils. Finally, the majority of promastigotes were killed by neutrophils, while axenic culture-and lesion-derived amastigotes were highly resistant to neutrophil microbicidal mechanisms. This study indicates that neutrophils exhibit distinct responses to promastigote and amastigote infection. Our findings have important implications for determining the impact of sustained neutrophil recruitment and amastigote-neutrophil interactions during the late phase of cutaneous leishmaniasis.

Recent studies have shown that histone proteins can act as antimicrobial peptides in host defense against extracellular bacteria, fungi, and Leishmania promastigotes. In this study, we used human recombinant histone proteins to further study their leishmaniacidal effects and the underlying mechanisms. We found that the histones H2A and H2B (but not H1(0)) could directly and efficiently kill promastigotes of Leishmania amazonensis, L. major, L. braziliensis, and L. mexicana in a treatment dose-dependent manner. Scanning electron microscopy revealed surface disruption of histone-treated promastigotes. More importantly, the preexposure of promastigotes to histone proteins markedly decreased the infectivity of promastigotes to murine macrophages (Mφs) in vitro. However, axenic and lesion-derived amastigotes of L. amazonensis and L. mexicana were relatively resistant to histone treatment, which correlated with the low levels of intracellular H2A in treated amastigotes. To understand the mechanisms underlying these differential responses, we investigated the role of promastigote surface molecules in histone-mediated killing. Compared with the corresponding controls, transgenic L. amazonensis promastigotes expressing lower levels of surface gp63 proteins were more susceptible to histone H2A, while L. major and L. mexicana promastigotes with targeted deletion of the lipophosphoglycan 2 (lpg2) gene (but not the lpg1 gene) were more resistant to histone H2A. We discuss the influence of promastigote major surface molecules in the leishmaniacidal effect of histone proteins. This study provides new information on host innate immunity to different developmental stages of Leishmania parasites.

Summary Leishmania parasites are the causative agents of leishmaniasis, a neglected tropical disease that causes substantial morbidity and considerable mortality in many developing areas of the world. Recent estimates suggest that roughly 10 million people suffer from cutaneous leishmaniasis (CL), and approximately 76 000 are afflicted with visceral leishmaniasis (VL), which is universally fatal without treatment. Efforts to develop therapeutics and vaccines have been greatly hampered by an incomplete understanding of the parasite's biology and a lack of clear protective correlates that must be met in order to achieve immunity. Although parasites grow and divide preferentially in macrophages, a number of other cell types interact with and internalize Leishmania parasites, including monocytes, dendritic cells and neutrophils. Neutrophils appear to be especially important shortly after parasites are introduced into the skin, and may serve a dual protective and permissive role during the establishment of infection. Curiously, neutrophil recruitment to the site of infection appears to continue into the chronic phase of disease, which may persist for many years. The immunological impact of these cells during chronic leishmaniasis is unclear at this time. In this review we discuss the ways in which neutrophils have been observed to prevent and promote the establishment of infection, examine the role of anti‐neutrophil antibodies in mouse models of leishmaniasis and consider recent findings that neutrophils may play a previously unrecognized role in influencing chronic parasite persistence.

Primary cutaneous marginal zone lymphoma (PCMZL) can be subdivided into 2 groups based on immunoglobulin (Ig) heavy chain usage: IgM-positive cases that constitute a less common and more T-helper type 1–driven process, and more common heavy chain class-switched cases that are predominantly T-helper type 2–driven. Although some report a significant IgG4-positive subset, others have found a much smaller proportion. To further evaluate the proportion of IgG4-positive PCMZL, to address whether IgG4-positive cases have any distinctive characteristics, and to assess whether additional features separating IgM-positive and class-switched cases could be identified, the clinicopathologic features of 26 PCMZL obtained from 19 patients were investigated. Twenty of 26 (77%) PCMZL were heavy chain class-switched (19 IgG-positive, 1 IgA-positive), including 9 that were IgG4-positive (35%). IgG4-positive and other class-switched PCMZL were morphologically similar. IgM-positive cases occurred in older individuals (median: 69 vs. 46.5 y; P=0.0001), more often involved the subcutis (P=0.002), demonstrated plasma cells diffusely scattered versus at the periphery of the lymphoid infiltrate (P=0.005), uniformly showed follicular colonization (P=0.0001), contained more numerous B cells (P=0.0004), and were more likely to have a T-cell CD4:CD8 ratio of <3:1 (P=0.03). None of the IgM-positive PCMZL harbored a MYD88 L265P mutation. No significant differences in clinical outcome were documented. These results highlight the high frequency of IgG4-positive PCMZL, which are otherwise similar to other class-switched cases, provide additional evidence supporting the distinction between class-switched and IgM-positive cases, and emphasize the indolent nature of at least the class-switched PCMZL, which may warrant their categorization as a clonal chronic lymphoproliferative disorder.

Summary Commensal flora plays an important role in the development of the mucosal immune system and in maintaining intestinal homeostasis. However, the mechanisms involved in regulation of host-microbiota interaction are still not completely understood. In this study, we examined how microbiota and intestinal inflammatory conditions regulate host microRNA expression and observed lower microRNA-107 (miR-107) expression in the inflamed intestines of colitic mice, compared with that in normal control mice. miR-107 was predominantly reduced in epithelial cells and CD11c+ myeloid cells including dendritic cells and macrophages in the inflamed intestines. We demonstrate that IL-6, IFN-γ and TNF-α downregulated, whereas TGF-β promoted, miR-107 expression. In addition, miR-107 expression was higher in the intestines of germ-free mice than in mice housed under specific pathogen-free conditions, and the presence of microbiota downregulated miR-107 expression in DCs and macrophages in a MyD88- and NF-κB-dependent manner. We determined that the ectopic expression of miR-107 specifically repressed the expression of IL-23p19, a key molecule in innate immune responses to commensal bacteria. We concluded that regulation of miR-107 by intestinal microbiota and pro-inflammatory cytokine serve as an important pathway for maintaining intestinal homeostasis.

Leishmania braziliensis and Leishmania amazonensis are both causative agents of cutaneous leishmaniasis in South America. However, patient prognosis and the host immune response differ considerably depending on the infecting parasite species. The mechanisms underlying these differences appear to be multifactorial, with both host and parasite components contributing to disease outcome. As neutrophils are a prominent component of the inflammatory infiltrate in chronic cutaneous, diffuse cutaneous and mucocutaneous lesions, we examined neutrophil activation and microbicidal activity against amastigotes of L. amazonensis and L. braziliensis. We found that murine neutrophils internalized L. braziliensis amastigotes with greater efficiency than did L. amazonensis amastigotes. Additionally, L. braziliensis infection was a potent trigger for neutrophil activation, oxidative burst, degranulation and the production of interleukin (IL)-22 and IL-10, while L. amazonensis amastigotes poorly induced these responses. Finally, neutrophils were able to kill L. braziliensis amastigotes, especially when cells were activated with phorbol myristate acetate. L. amazonensis amastigotes, however, were highly resistant to neutrophil microbicidal mechanisms. This study reveals, for the first time, differential neutrophil responsiveness to distinct species of Leishmania amastigotes and highlights the complexity of neutrophil-amastigote interactions during chronic leishmaniasis.

Background: It has been proposed that primary cutaneous marginal zone lymphomas (PCMZLs) include a MALT-lymphoma-like IgM+ subset and a class-switched subset, which is unlike most other MALT lymphomas. Whether expression of the MALT lymphoma-associated biomarkers IRTA1 and MNDA would support this concept and whether they might help explain why some patients have both subtypes is uncertain.Methods: Twenty-five PCMZLs from 21 patients were stained for IRTA1 by in situ hybridization and for MNDA by immunohistochemistry. In two patients, polymerase chain reaction (PCR)-based B-cell clonality studies were performed on biopsy specimens of metachronous lesions, which expressed different heavy chains. All results were correlated with the histopathologic and clinical findings.Results: Five of six IgM+ PCMZLs were IRTA1+ vs three of 18 evaluable classswitched cases (P = 0.0069). Two of the class-switched IRTA1+ cases were in patients with clonally-related IRTA1+ IgM+ PCMZLs. IRTA1 positivity showed a statistically significant correlation with several MALT-lymphoma-associated histopathologic findings. In contrast, all PCMZL cases showed at least some MNDA expression with no differences between IgM+ and class-switched cases.Conclusions: IRTA1 identifies MALT-lymphoma-like PCMZLs that are largely but not exclusively IgM+. This supports the concept of two PCMZL subsets but suggests their distinction should not be based solely on their heavy chain expression.