Abstract
The first formal description of the microbicidal activity of extracellular traps (ETs) containing DNA occurred in neutrophils in 2004. Since then, ETs have been identified in different populations of cells involved in both innate and adaptive immune responses. Much of the knowledge has been obtained from in vitro or ex vivo studies; however, in vivo evaluations in experimental models and human biological materials have corroborated some of the results obtained. Two types of ETs have been described—suicidal and vital ETs, with or without the death of the producer cell. The studies showed that the same cell type may have more than one ETs formation mechanism and that different cells may have similar ETs formation mechanisms. ETs can act by controlling or promoting the mechanisms involved in the development and evolution of various infectious and non-infectious diseases, such as autoimmune, cardiovascular, thrombotic, and neoplastic diseases, among others. This review discusses the presence of ETs in neutrophils, macrophages, mast cells, eosinophils, basophils, plasmacytoid dendritic cells, and recent evidence of the presence of ETs in B lymphocytes, CD4+ T lymphocytes, and CD8+ T lymphocytes. Moreover, due to recently collected information, the effect of ETs on COVID-19 is also discussed.
Highlights
Laboratory of Immunoparasitology, Oswaldo Cruz Institute (IOC), Fundação Oswaldo Cruz (Fiocruz), Postgraduate Program in Clinical Research in Infectious Diseases, INI-Fiocruz, Rio de Janeiro 21.040-360, RJ, Brazil
Since most of the studies showed that MCETs formation is reactive oxygen species (ROS)-dependent and that pathogens can induce different Mast cells (MCs) responses, Garcia-Rodrigues et al analyzed the response pattern of human MCs obtained from blood mononuclear cells and differentiated in vitro according to DNA and chemokine release, degranulation, and the presence or absence of ROS vis-à-vis pathogens from different tissues
All these years of studies and data collection on ETs identify a variety of cell types involved, as well as formation mechanisms and potential actions of releasing extracellular traps upon protection and disease
Summary
With the great impetus given to the understanding of cellular functions in the immune system in the early 1950s, much information has been obtained; some mechanisms have not yet been fully elucidated. This knowledge is crucial to understand the mechanisms of disease and/or protection, since knowing how to recognize in what way diseases occur develop new treatments and effective vaccines with fewer adverse effects. The mechanisms described are varied and can be identified as inhibitors or facilitators of lesions, and some recent publications describe details of the ETs formation, their mechanisms, and structure [2,3,4,5]. Some mechanisms and effects of ETs release still need further elucidation, what is already known shows the importance of ETs in the control and/or development of the immune response
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