Neutrophil and eosinophil ETosis-mediated extracellular trap formation in a patient with chronic granulomatous disease

The underrated immune role of bivalve 'serous cells': New insight from inflammatory responses of the Manila clam Ruditapes philippinarum

This study investigated the immune role of serous cells from the bivalve Ruditapes philippinarum. Histochemical and immunohistochemical assays revealed that the serous cells contained large cytoplasmic vacuoles rich in heparinoid molecules. Heparin and histamine were detected within vacuoles, with distinct spatial distributions, and histoenzymatic assays for serine proteases revealed both tryptase and chymase activity. These findings, together with membrane immunolabelling for c-kit, suggest similarities with vertebrate mast cells. After in vivo bacterial inoculation, serous cells first accumulated at the injury site within 12 h, and 15 h after in vitro treatment, a significant increase in the percentage of serous cells was observed in bacteria-treated samples, supporting targeted responses of proliferation and differentiation following bacterial challenge. Serous cells also underwent marked degranulation following bacterial stimulation, and aggregates of granulocytes, hyalinocytes and serous cells appeared within 1 h of treatment. Extracellular trap formation (ETosis), which is rich in degranulated serous cells and trapped dying bacteria, was observed after 15 h. Serous cells showed nuclear envelope loss and chromatin fragmentation. The extracellular nets were primarily composed of fragmented chromatin and amyloid fibrils forming a scaffold of woven fibres, to which the adhesion of heparin, histamine, and serine proteases occurred after their release into the extracellular environment. To our knowledge, this is the first study that highlights the important role of serous cells in the immune response of bivalves and provides new perspectives for future investigations into the modulation of the inflammatory process.

Eosinophilic mucus diseases

Eosinophilic inflammation is primarily characterized by type 2 immune responses against parasitic organisms. In the contemporary human being especially in developed countries, eosinophilic inflammation is strongly associated with allergic/sterile inflammation, and constitutes an undesired immune reaction. This situation is in stark contrast to neutrophilic inflammation, which is indispensable for the host defense against bacterial infections. Among eosinophilic inflammatory disorders, massive accumulation of eosinophils within mucus is observed in certain cases, and is often linked to the distinctive clinical finding of mucus with high viscosity. Eosinophilic mucus is found in a variety of diseases, including chronic allergic keratoconjunctivitis, chronic rhinosinusitis encompassing allergic fungal sinusitis, eosinophilic otitis media, eosinophilic sialodochitis, allergic bronchopulmonary aspergillosis/mycosis, eosinophilic plastic bronchitis, and eosinophilic asthma. In these pathological conditions, chronic inflammation and tissue remodeling coupled with irreversible organ damage due to persistent adhesion of toxic substances and luminal obstruction may impose a significant burden on the body. Eosinophils aggregate in the hyperconcentrated mucus together with cell-derived crystals, macromolecules, and polymers, thereby affecting the biophysical properties of the mucus. This review focuses on the clinically significant challenges of mucus and discusses the consequences of activated eosinophils on the mucosal surface that impact mucus and persistent inflammation.