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Transient neutropenia: neutrophil distribution and replacement
1Department of Radiology, Thomas Jefferson University Hospital, Philadelphia, Pennsylvania 19107, USA.
Summary
Radiolabeled agents for imaging inflammation can cause neutropenia (low white blood cell count). This study shows neutropenia severity and duration depend on the dose, and lost white blood cells sequester in organs, not returning to circulation.
Area of Science:
- Immunology
- Nuclear Medicine
- Pharmacology
Background:
- Radiolabeled receptor-specific proteins and peptides are investigated for imaging inflammatory foci.
- Some imaging agents can induce transient neutropenia, a decrease in neutrophils (a type of white blood cell).
Observation:
- This study quantified the dose-dependent relationship between monoclonal antibody (MAb) administration and neutropenia in mice.
- Neutrophil recovery time was also dose-dependent, with higher doses leading to longer recovery periods.
Findings:
- Neutropenia severity increased with MAb dose, with over 95% neutrophil loss at 150 micrograms.
- Recovered neutrophil counts did not correlate with restored blood activity, suggesting sequestered neutrophils do not re-enter circulation.
- Radioactivity decreased in most organs over time, except the liver and spleen, indicating neutrophil sequestration in the reticuloendothelial system.
Implications:
- The degree and duration of neutropenia are directly related to the administered dose of the imaging agent.
- Neutrophils lost during imaging sequester in the liver and spleen and are not available for subsequent imaging.
- Neutrophil counts are restored by fresh release from bone marrow, not by the return of sequestered cells.