NETosis is a unique form of cell death that is characterized by the release of decondensed chromatin and granular contents to the extracellular space. The initial observation of NETosis placed the process within the context of the innate immune response to infections. Neutrophils, the most numerous leukocytes that arrive quickly at the site of an infection, were the first cell type shown to undergo extracellular trap formation. However, subsequent studies showed that other granulocytes are also capable of releasing nuclear chromatin following stimulation. The extracellular chromatin acts to immobilize microbes and prevent their dispersal in the host. Bacterial breakdown products and inflammatory stimuli induce NETosis and the release of NETs requires enzyme activities. Histones in NET chromatin become modified by peptidylarginine deiminase 4 (PAD4) and cleaved at specific sites by proteases. NETs serve for attachment of bactericidal enzymes including myeloperoxidase, leukocyte proteases, and the cathelicidin LL-37. While the benefit of NETs in an infection appears clear, NETs also figure prominently at the center of various pathologic states. Therefore, it is important for NETs to be efficiently cleared; else digestive enzymes may gain access to tissues where inflammation takes place. Persistent NET exposure at sites of inflammation may lead to a further complication: NET antigens may provoke acquired immune responses and, over time, could initiate autoimmune reactions. Recent studies identified aberrant NET synthesis and/or clearance in inflammatory/autoimmune conditions such as systemic lupus erythematosus (SLE), psoriasis, ANCA-positive vasculitis, gout and Felty’s syndrome. In the case of SLE, for example, it appears that LL-37 exposed in the NETs may be a significant trigger of type I Interferon responses in this disease. Recent evidence also implicates aberrant NET formation in the development of endothelial damage, atherosclerosis and thrombosis. NETosis is thus of interest to researchers who investigate innate immune responses, host-pathogen interactions, chronic inflammatory disorders, cell and vascular biology, biochemistry, and autoimmunity. As we approach the 10-year-anniversary of the initial discovery of NETosis, it is useful and timely to review the so far identified mechanisms and pathways of NET formation, their role in bacterial and fungal defense and their putative importance as inducers of autoimmune responses. We look forward to a rich and rigorous discussion of these and related issues that benefit from interdisciplinary approaches, collaborations and exciting discoveries.

This book is a printed edition of the Special Issue "Identification and Characterization of Antimicrobial Peptides with Therapeutic Potential" that was published in Pharmaceuticals

This book highlights the important role of neutrophils in health as well as in the pathogenesis of various diseases. Section 1 provides a general background information regarding the mechanisms and various triggers of neutrophil extracellular traps (NETs) formation and their role in various infectious and noninfectious diseases (such as postinjury inflammation). Section 2 provides recent evidence regarding the role of neutrophils in the pathogenesis as well as a therapeutic target for selected disease conditions such as periodontal diseases, rheumatoid arthritis, and cystic fibrosis. Section 3 describes the anti-inflammatory properties of neutrophils with focus regarding their role in graft versus host disease. This book provides a wider picture with regard to the importance of this immune cell type in various diseases with focus on one of its recently discovered properties, NETs. Therapeutic targets aimed to modulate neutrophil functions might provide novel approaches in the treatment of various diseases of infectious and noninfectious origin.

NETosis, a form of cell death that manifests by the release of decondensed chromatin to the extracellular space, provides valuable insights into mechanisms and consequences of cellular demise. Because extracellular chromatin can immobilize microbes, the extended nucleohistone network was called a neutrophil extracellular trap (NET), and the process of chromatin release was proposed to serve an innate immune defense function. Extracellular chromatin NETs were initially observed in studies of neutrophils and are most prominent in these types of granulocytes. Subsequent studies showed that other granulocytes and, in a limited way, other cells of the innate immune response may also release nuclear chromatin following certain kinds of stimulation. Variations of NETosis were noted with cells that remain temporarily motile after the release of chromatin. Numerous stimuli for NETosis were discovered, including bacterial breakdown products, inflammatory stimuli, particulate matter, certain crystals, immune complexes and activated thrombocytes. Fundamental explorations into the mechanisms of NETosis observed that neutrophil enzyme activity (PAD4, neutrophil elastase, proteinase 3 and myeloperoxidase) and signal transduction pathways contribute to the regulation of NETosis. Histones in NET chromatin become modified by peptidylarginine deiminase 4 (PAD4) and cleaved at specific sites by proteases, leading to extensive chromatin externalization. In addition, NETs serve for attachment of bactericidal enzymes including myeloperoxidase, leukocyte proteases, and the cathelicidin LL-37. NETs are decorated with proteases and may thus contribute to tissue destruction. However, the attachment of these enzymes to NET-associated supramolecular structures restricts systemic spread of the proteolytic activity. While the benefit of NETs in an infection appears obvious, NETs also participate as key protagonists in various pathologic states. Therefore, it is essential for NETs to be efficiently cleared; otherwise digestive enzymes may gain access to tissues where inflammation takes place. Persistent NET exposure at sites of inflammation may lead to a further complication: NET antigens may provoke acquired immune responses and, over time, could initiate autoimmune reactions, serve as antigen for nuclear autoantibodies and foster DNA immune complex-related inflammation. Neutrophil products and deiminated proteins comprise an important group of autoantigens in musculoskeletal disorders. Aberrant NET synthesis and/or clearance are often associated with inflammatory and autoimmune conditions. Recent evidence also implicates aberrant NET formation in the development of endothelial damage, atherosclerosis and thrombosis. Intravital microscopy provides evidence for conditions that induce NETosis in vivo. Furthermore, NETs can easily be detected in synovial fluid and tissue sections of patients with arthritis and gout. NETosis is thus of interest to researchers who investigate innate immune responses, host-pathogen interactions, chronic inflammatory disorders, cell and vascular biology, biochemistry, and autoimmunity. As we enter the second decade of research on NETosis, it is useful and timely to review the mechanisms and pathways of NET formation, their role in bacterial and fungal defense and their importance as inducers of autoimmune responses.

Contains papers from a July 1998 conference held at the Queens College Campus of the City University of New York. Papers are arranged in sections on mechanisms and general considerations, programmed (developmental) cell death, and cell death and pathological and clinical situations. Specific topics

Candida, which was discovered more than a century ago as a causative organism of oral thrush, is now thought to potentially infect almost every tissue of the human body. Although we still do not have a safe anti-candida drug, the growing pace of progess of research on Candida albicans holds promise that a breakthrough is imminent. Though many monographs and articles on candida and candidoses have appeared in recent years, they mostly cover the clinical aspects. This particular text, however, explains the more basic features of candida including the molecular genetics, molecular biology and immunology of the cell wall, the molecular basis of morphogenesis and the structure and function of the plasma membrane. The role of anti-candida drugs and their mechanism of action are also discussed.

The book starts with dissecting mechanisms underlying viral immune evasion via exploiting the host complement system by vaccinia virus, and by modulating the type 1 interferon response by RNA viruses. Yet another chapter looks into how viroporins expressed by different families of viruses causing influenza A virus, SARS, hepatitis C and HIV interact with several cellular pathways. Understanding of these mechanisms can aid the development of novel potential anti‐viral targets. The chapter on tuberculosis discusses the emerging importance of the innate immune mechanisms against Mycobacterium tuberculosis infection and latency. This book has a strong focus on fungal pathogenesis and immunity, starting with virulence and host factors that attain great importance in candidiasis and associated escape tricks of seriously opportunistic fungi. Two chapters on Aspergillus fumigatus elaborate on the pathogenic mechanisms: first discussing A. fumigatus‐airway epithelium interaction, followed by fungal and host factors that are paramount in the development of allergic and invasive aspergillosis. In the subsequent chapter, there is a general discussion on the innate and adaptive immune responses against primary and opportunistic fungal pathogens.