Microbes and the fate of neutrophils

Abstract

Summary Neutrophils or polymorphonuclear neutrophils (PMNs) are an important component of innate host defense. These phagocytic leukocytes are recruited to infected tissues and kill invading microbes. There are several general characteristics of neutrophils that make them highly effective as antimicrobial cells. First, there is tremendous daily production and turnover of granulocytes in healthy adults—typically 1011 per day. The vast majority (~95%) of these cells are neutrophils. In addition, neutrophils are mobilized rapidly in response to chemotactic factors and are among the first leukocytes recruited to infected tissues. Most notably, neutrophils contain and/or produce an abundance of antimicrobial molecules. Many of these antimicrobial molecules are toxic to host cells and can destroy host tissues. Thus, neutrophil activation and turnover are highly regulated processes. To that end, aged neutrophils undergo apoptosis constitutively, a process that contains antimicrobial function and proinflammatory capacity. Importantly, apoptosis facilitates nonphlogistic turnover of neutrophils and removal by macrophages. This homeostatic process is altered by interaction with microbes and their products, as well as host proinflammatory molecules. Microbial pathogens can delay neutrophil apoptosis, accelerate apoptosis following phagocytosis, or cause neutrophil cytolysis. Here, we review these processes and provide perspective on recent studies that have potential to impact this paradigm.

Expression and significance of ELANE and CTSG in primary acquired nasolacrimal duct obstruction

“…Tears from PANDO patients were found to contain a large number of differentially expressed proteins (369 in total) compared to those from healthy subjects, and most of these proteins are involved in inflammatory responses and immune-related signaling pathways, consistent with the results of cytokine assays in previous studies. 19 Many previous studies on PANDO focused on the pathological alterations of the patient's nasolacrimal ducts, mainly showing inflammatory and fibrotic processes, 20 which are consistent with the proteomic findings. Combining the results of pathological alterations and bioinformatics analysis, we screened for two proteins that are significantly upregulated in the tears of PANDO patients and closely associated with inflammatory and fibrotic processes, ELANE and CTSG, for follow-up studies.…”

Spatiotemporal transcriptomic profiling reveals the dynamic immunological landscape of alveolar echinococcosis

“…Interestingly, genes related to the negative regulation of the immune system ( Arg2, Cd274 ) were also enriched in Il1b hi Neu (Figure 3G), indicating the anti-inflammatory feedback of these cells. The Il1b hi Neu, with higher apoptotic signatures, might be more prone to be engulfed by phagocytes 31 . Comparatively, the Mpo hi Neu displayed a gene expression signature suggestive of innate antibacterial immunity ( Camp , Ltf , Elane ) and defense response to pathogens ( Ngp ) (Figure 3G).…”

Insights into innate immune cell evasion by Chlamydia trachomatis

“…Neutrophil (NE) is the most abundant innate immune cells and the first leukocytes recruited to infected tissues. Neutrophils kill microorganisms primarily by phagocytosis and activation of the NADPH oxidase machinery ( 67 ). When neutrophils encounter pathogens, they activate their bactericidal reservoir to produce reactive oxygen species (ROS) and neutrophil extracellular traps (NETs).…”