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Emperipolesis of neutrophils by dysmorphic megakaryocytes
Abstract:
Neutrophil engulfment by megakaryocytes was observed within 20 to 30% of megakaryocytes from two children: one with metastatic rhabdomyosarcoma, the other with fever of unknown origin. Other cell types and neutrophil precursors were not observed within megakaryocytes. Only late megakaryocytes were involved in the process, and often these cells appeared vacuolated or degenerating at the light and electron microscope level. Ultrastructurally the engulfed neutrophils were intact and were within the open canalicular system of the megakaryocyte cytoplasm. No evidence of neutrophil granule exocytosis could be demonstrated in ultrastructural morphologic and peroxidase preparations; however, many neutrophils appeared to be endocytosing portions of the megakaryocyte cytoplasm. The phenomenon could not be transferred to normal marrow incubated with patient serum or plasma. Thus, our patients differ from previous observations of emperipolesis in: 1) the extreme frequency of the observation; 2) the selective involvement of neutrophils; and 3) the association of the anomaly with dysmorphic and/or disrupted megakaryocytes. These observations are consistent with a neutrophil response to altered and/or injured megakaryocytes.
Insights
Neutrophils were engulfed by damaged megakaryocytes in two children, a rare event not seen in healthy individuals. This suggests neutrophils may respond to injured megakaryocytes.
Area of Science:
- Hematology
- Cell Biology
- Pathology
Background:
- Emperipolesis, the interaction of hematopoietic cells within other hematopoietic cells, is a known phenomenon.
- Previous studies have described emperipolesis involving various cell types, but not specifically neutrophils interacting with damaged megakaryocytes.
Observation:
- Neutrophil engulfment by megakaryocytes was observed in 20-30% of megakaryocytes from two pediatric patients.
- The affected megakaryocytes were late-stage, often appearing vacuolated or degenerating.
- Engulfed neutrophils remained intact within the megakaryocyte's open canalicular system, with some neutrophils appearing to endocytose megakaryocyte cytoplasm.
Findings:
- This phenomenon was highly frequent and selectively involved neutrophils.
- The interaction was associated with dysmorphic and disrupted megakaryocytes.
- The process could not be transferred to normal marrow via patient serum or plasma, indicating a cell-intrinsic or local microenvironment effect.
Implications:
- These findings suggest a novel form of emperipolesis where neutrophils actively respond to injured or altered megakaryocytes.
- This interaction may represent a unique cellular defense or clearance mechanism in specific pathological conditions.
- Further research is needed to elucidate the precise molecular mechanisms and clinical significance of this neutrophil-megakaryocyte interaction.