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Activated human B cells produce phospholipase D4-containing extracellular vesicles

Tsubasa Betsuyaku1, Shuji Akizuki1, Yihan Liu1

  • 1Department of Rheumatology and Clinical Immunology, Graduate school of Medicine, Kyoto University, Kyoto, Japan.

Plos One
|August 14, 2025
PubMed

Insights

Activated B cells release the immune-regulating enzyme Phospholipase D4 (PLD4) within extracellular vesicles (EVs). This discovery reveals a new pathway for PLD4

Area of Science:

  • Immunology
  • Cell Biology
  • Molecular Biology

Background:

  • Phospholipase D4 (PLD4) is an intracellular exonuclease involved in immune responses through nucleic acid degradation.
  • Existing data suggest PLD4 is present in human plasma, but its extracellular release mechanism is unknown.

Purpose of the Study:

  • To investigate the cellular origin and mechanism of extracellular Phospholipase D4 (PLD4) release.
  • To determine if activated B cells secrete PLD4 via extracellular vesicles (EVs).

Main Methods:

  • Purification and analysis of EVs from human plasma using immunoelectron microscopy (IEM), Western blotting, and ELISA.
  • In vitro stimulation of human B cells and analysis of cellular changes and EV secretion using microscopy and Nanoparticle Tracking Analysis (NTA).
  • Immunofluorescence and IEM to track PLD4 localization within stimulated B cells.

Main Results:

  • Human plasma EVs were confirmed to contain PLD4.
  • Stimulated B cells exhibited hypertrophy, increased multivesicular bodies, and enhanced EV secretion.
  • PLD4 was observed to translocate to endosomes and be incorporated into EVs released by activated B cells.

Conclusions:

  • Activated B cells secrete PLD4 via extracellular vesicles (EVs), establishing a novel mechanism for its extracellular presence.
  • This secretion pathway highlights a potential role for B cell-derived EVs in intercellular communication and immune regulation.
  • PLD4's release through EVs suggests new avenues for understanding its function in immunity.

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