Swimming Motility Mediates the Formation of Neutrophil Extracellular Traps Induced by Flagellated Pseudomonas aeruginosa.

Pseudomonas aeruginosa is an opportunistic pathogen causing severe infections often characterized by robust neutrophilic infiltration. Neutrophils provide the first line of defense against P. aeruginosa. Aside from their defense conferred by phagocytic activity, neutrophils also release neutrophil extracellular traps (NETs) to immobilize bacteria. Although NET formation is an important antimicrobial process, the details of its mechanism are largely unknown. The identity of the main components of P. aeruginosa responsible for triggering NET formation is unclear. In this study, our focus was to identify the main bacterial factors mediating NET formation and to gain insight into the underlying mechanism. We found that P. aeruginosa in its exponential growth phase promoted strong NET formation in human neutrophils while its NET-inducing ability dramatically decreased at later stages of bacterial growth. We identified the flagellum as the primary component of P. aeruginosa responsible for inducing NET extrusion as flagellum-deficient bacteria remained seriously impaired in triggering NET formation. Purified P. aeruginosa flagellin, the monomeric component of the flagellum, does not stimulate NET formation in human neutrophils. P. aeruginosa-induced NET formation is independent of the flagellum-sensing receptors TLR5 and NLRC4 in both human and mouse neutrophils. Interestingly, we found that flagellar motility, not flagellum binding to neutrophils per se, mediates NET release induced by flagellated bacteria. Immotile, flagellar motor-deficient bacterial strains producing paralyzed flagella did not induce NET formation. Forced contact between immotile P. aeruginosa and neutrophils restored their NET-inducing ability. Both the motAB and motCD genetic loci encoding flagellar motor genes contribute to maximal NET release; however the motCD genes play a more important role. Phagocytosis of P. aeruginosa and superoxide production by neutrophils were also largely dependent upon a functional flagellum. Taken together, the flagellum is herein presented for the first time as the main organelle of planktonic bacteria responsible for mediating NET release. Furthermore, flagellar motility, rather than binding of the flagellum to flagellum-sensing receptors on host cells, is required for P. aeruginosa to induce NET release.

Clear Cell Odontogenic Carcinoma: A Series of Three Cases.

BACKGROUND: Clear cell odontogenic carcinoma (CCOC) is a rare malignant odontogenic epithelial neoplasm of the jaws. It is composed of irregular nests of clear to faintly eosinophilic cells resembling clear cell rests of primitive dental lamina and an intermixed hyalinized fibrous stroma. Most cases occur in the 5th and 6th decades of life, with a female predominance. The mandible is affected more than the maxilla. Clinical features vary from asymptomatic to non-specific pain, ill-defined radiolucency, root resorption, and sometimes soft tissue extension. Histology varies from bland to high grade. CCOC demonstrated a significant tendency to recur. Metastasis typically involves regional lymph nodes, which haves been reported in 20-25% of cases. Pulmonary metastasis rarely occurs. Differential diagnoses are broad and include odontogenic, salivary, melanocytic, and metastatic neoplasia. CCOCs are positive for cytokeratins, mainly AE1/AE3 and CK19. Most cases show EWSR1 rearrangement and rarely, the BRAFV600E mutation. DESIGN: Patient charts were reviewed at our institution. A total of three cases were found in electronic medical records, which were diagnosed as clear cell odontogenic carcinoma over a period of six years (2014-2019). Patient charts were reviewed for medical history and radiology data. The pathology slides were reviewed by one or more faculty members. RESULTS: We present three cases of CCOC, ranging in age from 40 to 69 years (two women and one man). Two cases involved the maxilla and one involved the mandible. Two presented with painful swelling and one with mass recurrence. Radiography results show that two had poorly defined radiolucent lesions, and one was heterogeneous with a small nodule projecting into the maxillary sinus. Histological examination revealed an epithelial neoplasm composed of irregular sheets, cords, and nests of polygonal cells with central hyperchromatic, mildly pleomorphic nuclei surrounded by clear to pale eosinophilic cytoplasm, with occasional mitotic figures. The tumor had infiltrated the bone and soft tissues. Two cases were immunopositive for CK5/6 and one case was positive for p63 and CK19. Interestingly, the eosinophilic dentinoid matrix interspersed among tumor cells in one case was consistent with its odontogenic origin. Histochemical staining showed PAS-positive and diastase-labile intracytoplasmic material consistent with glycogen. CONCLUSION: Our study highlights the potential diagnostic significance of dentinoid (although reportedly seen in only 7% of cases), along with CK5/6 immunopositivity, in supporting the histologic diagnosis of CCOC among a variety of neoplasia in its differential diagnosis.