Donor platelets stored for at least 3 days can elicit activation marker expression by the recipient's blood mononuclear cells: an in vitro study

BACKGROUND: Recent studies have demonstrated that infused platelets (PLTs) can promote inflammation. The objective of this study was to evaluate the impact of storage of transfusion-grade PLTs on the peripheral blood mononuclear cells (PBMNCs) of the recipient. STUDY DESIGN AND METHODS: An in vitro cell model system was established to measure the degree of activation of donor PLTs during 5 days of their storage and then to measure immune cell activation by detecting marker expression in coculture experiments. RESULTS: The level of soluble CD62p increased significantly by Day 3, and membrane expression of CD62p increased significantly from Day 2, indicating some degree of PLT activation over time during storage (p < 0.05). Donor PLTs and PBMNC subsets (monocytes, B cells, and T cells) from recipients were cocultured for 48 hours. The number of PLT-PBMNC subset doublets detected by flow cytometry was correlated with the PLT storage time after Day 3 (p < 0.05), indicating consistent binding of PLTs to PBMNCs. The results of these experiments showed that there was a consistent and significant increase in expression of conventional activation markers of T cells, B cells, and monocytes compared with appropriate controls (p < 0.05 to < 0.01). CONCLUSION: The results of this study indicate that, from Day 3 onward, activation markers are consistently expressed on PLTs. From these results, we conclude that activated PLTs may affect PBMNC interactions in recipients.