Nikhil Prasad Fact checked by:Thailand Medical News Team Sep 27, 2026 44 minutes ago
Tiny biological particles accumulating in stored red blood cell concentrates may influence immune responses after transfusion, with new laboratory research showing that these particles can stimulate the proliferation of important T cells.
Exosomes accumulating in stored red blood cell concentrates may alter T cell responses, with leukoreduction
appearing to reduce their immune-stimulating effects
A new study examined exosomes—small extracellular vesicles capable of carrying proteins and other biological signals—and their possible contribution to transfusion-related immunomodulation (TRIM), the immune changes that can follow allogeneic blood transfusion.
Researchers Test Stored Blood
Researchers obtained red blood cell concentrates from six healthy donors and divided each donation into leukoreduced and non-leukoreduced units. Leukoreduction removes most white blood cells and is widely used to reduce transfusion-related complications.
Samples were stored for up to 42 days. Exosomes were isolated and tested at doses of 0.2, 1 and 5 micrograms in cultures containing peripheral blood mononuclear cells. T cell proliferation and regulatory T cells, or Tregs, were then measured using flow cytometry.
The researchers were from the Dr. Raşit DURUSOY Blood Bank, Faculty of Medicine; Department of Immunology, Faculty of Medicine; Experimental Animal Breeding and Research Unit, Faculty of Medicine; Experimental and Molecular Immunology Laboratory; Department of Medicine-Immunology, Institute of Health Science; Department of Virology, Faculty of Veterinary Medicine; and Department of Infectious Diseases and Clinical Microbiology, Faculty of Medicine—all at Bursa Uludag University, Türkiye.
Exosomes Increased as Blood Was Stored
One striking finding was that exosomal protein accumulated during storage. In non-leukoreduced samples, levels on days 21 and 42 were significantly higher than on day zero. Leukoreduced samples showed a smaller increase, although day-42 levels remained significantly above baseline.
More importantly, this
Thailand Medical News report highlights evidence that exosomes from non-leukoreduced blood significantly increased both CD4+ and CD8+ T cell proliferation, particularly under allogeneic conditions.
CD4+ proliferation increased significantly in allogeneic cultures and with non-leukoreduced exosomes. CD8+ proliferation also rose significantly, with particularly strong differences for allogeneic and non-leukoreduced conditions. Leukoreduction reduced these proliferative effects.
Regulatory T Cells Tell a Different Story
Exosomes did not generally expand Tregs. Instead, autologous cultures showed significantly reduced CD8+ Tregs and CD39-expressing CD8+ Tregs, while several other Treg measurements showed downward trends.
Conclusions
The findings suggest that exosomes accumulating in stored red blood cell products can influence immune activity, particu
larly by promoting effector T cell proliferation. However, the effects depend strongly on leukoreduction and whether exposure is allogeneic or autologous, and laboratory findings require further investigation before their clinical importance can be established.
The study findings were published in the peer reviewed Journal of Clinical Medicine.
https://www.mdpi.com/2077-0383/15/19/7501
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https://www.thailandmedical.news/articles/immunology 
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