Perforin-2 (MPEG1) is a pore-forming, antibacterial protein with broad-spectrum activity. Perforin-2 is expressed constitutively in phagocytes and inducibly in parenchymal, tissue-forming cells. In vitro, Perforin-2 prevents the intracellular replication and proliferation of bacterial pathogens in these cells. Perforin-2 knockout mice are unable to control the systemic dissemination of methicillin-resistant Staphylococcus aureus (MRSA) or Salmonella typhimurium and perish shortly after epicutaneous or orogastric infection respectively. In contrast, Perforin-2-sufficient littermates clear the infection. Perforin-2 is a transmembrane protein of cytosolic vesicles -derived from multiple organelles- that translocate to and fuse with bacterium containing vesicles. Subsequently, Perforin-2 polymerizes and forms large clusters of 100 Å pores in the bacterial surface with Perforin-2 cleavage products present in bacteria. Perforin-2 is also required for the bactericidal activity of reactive oxygen and nitrogen species and hydrolytic enzymes. Perforin-2 constitutes a novel and apparently essential bactericidal effector molecule of the innate immune system.DOI: http://dx.doi.org/10.7554/eLife.06508.001

Diabetic foot ulcers (DFUs) are a life-threatening disease that often result in lower limb amputations and a shortened lifespan. However, molecular mechanisms contributing to the pathogenesis of DFUs remain poorly understood. We use next-generation sequencing to generate a human dataset of pathogenic DFUs to compare to transcriptional profiles of human skin and oral acute wounds, oral as a model of “ideal” adult tissue repair due to accelerated closure without scarring. Here we identify major transcriptional networks deregulated in DFUs that result in decreased neutrophils and macrophages recruitment and overall poorly controlled inflammatory response. Transcription factors FOXM1 and STAT3, which function to activate and promote survival of immune cells, are inhibited in DFUs. Moreover, inhibition of FOXM1 in diabetic mouse models (STZ-induced and db/db) results in delayed wound healing and decreased neutrophil and macrophage recruitment in diabetic wounds in vivo. Our data underscore the role of a perturbed, ineffective inflammatory response as a major contributor to the pathogenesis of DFUs, which is facilitated by FOXM1-mediated deregulation of recruitment of neutrophils and macrophages, revealing a potential therapeutic strategy.

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IntroductionConvincing evidence exists for a protective role of cellular immunity in HIV infection. For example, virologic control and detection of HIV-specific cytotoxic T lymphocytes (CTLs) are temporally related during primary HIV infection, 1 and CD8 T-cell depletion results in widespread virus replication and disease progression in the simian immunodeficiency virus (SIV)-infected nonhuman primate model. In HIV infection, the failure of antiviral immunity has been attributed in part to qualitative CTL defects 2-4 such as decreased perforin in total-and HIV-specific CD8 T cells in peripheral blood and lymphoid tissue, including gutassociated lymphoid tissues. [5][6][7][8] Perforin defects are also evident in CTLs of patients who are on highly active antiretroviral therapy (HAART). 2,9 The inability of most patients to keep HIV under control in the absence of potent antiretroviral therapy 10,11 has led to the quest for immunotherapeutic approaches to augment antiviral cellular immunity.CD8 T cells can be identified phenotypically for their maturation status based upon expression of cell-surface maturation markers. For example, naive, central memory, effector memory, and effector subsets manifest differential expression of CD45RA and CD62L or CCR7, 12 and perturbations in their distribution have been identified in HIV infection. Typically, naive and effector CD8 T cells are reduced, and effector memory subsets are expanded in patients with HIV who have only partial restoration with HAART. [1][2][3] The major mechanism by which effector CD8 T cells kill virusinfected targets and tumor cells is via secretion of lytic molecules, namely perforin and granzymes. 13,14 Lytic granules in CTLs are stored in a dense core within secretory lysosomes, 15 and the membrane that encloses the granules contains lysosomal glycoproteins such as lysosome-associated membrane protein-1 (LAMP-1; CD107a), LAMP-2 (CD107b), and CD63. 16 Soluble granule contents are released during exocytosis, and the incorporation of granule membrane proteins such as CD107a into the plasma membrane serve as markers of degranulation.Preservation of memory and effector CD8 T-cell pools in vivo depends in part upon homeostatic proliferation which is regulated by cytokines and self-peptide MHC ligands for the T-cell receptor (TCR). It is now widely accepted that generation of long-term memory CD4 and CD8 T cells is dependent upon antigenic stimulation, but their survival is antigen independent and requires peripherally produced cytokines, particularly those that use the common ␥-chain for signaling, such as interleukin (IL)-15. [17][18][19] Another more recently described pleiotropic cytokine that uses the common ␥-chain is IL-21, which is produced only by activated CD4 T lymphocytes and has significant sequence similarity to cytokines IL-2, Based on the known T-cell-potentiating properties of IL-21 in tumor models, 26,27 we hypothesized that IL-21 could augment the effector function of CD8 T cells in patients with HIV. Patients, materials, and methods Stu...

The skin microbiota is intimately coupled with cutaneous health and disease. Interactions between commensal microbiota and the multiple cell types involved in cutaneous wound healing regulate the immune response and promote barrier restoration. This dialog between host cells and the microbiome is dysregulated in chronic wounds. In this review, we first describe how advances in sequencing approaches and analysis have been used to study the chronic wound microbiota, and how these findings underscored the complexity of microbial communities and their association with clinical outcomes in patients with chronic wound disorders. We also discuss the mechanistic insights gathered from multiple animal models of polymicrobial wound infections. In addition to the well-described role of bacteria residing in polymicrobial biofilms, we also discuss the role of the intracellular bacterial niche in wound healing. We describe how, in contrast to pathogenic species capable of subverting skin immunity, commensals are essential for the regulation of the cutaneous immune system and provide protection from intracellular pathogens through modulation of the antimicrobial molecule, Perforin-2. Despite recent advances, more research is needed to shed light on host-microbiome crosstalk in both healing and nonhealing chronic wounds to appropriately guide therapeutic developments.