Influence of ex vivo-storage on toll-like receptor-mediated mechanisms in human platelets

• Applicant: Privatdozent Dr. Jürgen Kößler
• Subject Area: Hematology, Oncology ; Clinical Immunology and Allergology
• Term: since 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 527322478

In addition to hemostasis, platelets are also relevantly involved in immunological processes. On the platelet surface membrane, receptors are expressed as part of innate immunity, allowing the recognition of “damage-“ or “pathogen-associated patterns” (DAMPs, PAMPs). These include toll-like receptors (TLR), among them the most expressed TLR2 and TLR4. The activation of platelet TLR4 is linked to the formation of „neutrophil extracellular traps“ (NETs), associated with the occurence of the severe transfusion-associated reaction TRALI (transfusion-related acute lung injury). Furthermore, platelets are able to shed stored mediators from granules upon TLR activation, thereby influencing leukocyte reactions and potentially triggering transfusion reactions. Therefore, The consecutive analysis of TLR-associated mechanisms playing a role in platelet transfusion, is in the focus of this project. In previous studies, it came apparent that the plasma content of the surrounding milieu interferes with TLR2- or TLR4-induced aggregation or chemokine release of platelets. In the intended project, the influence of storage time and storage temperature (4 ± 2°C or 22 ± 2°C) on TLR2- and TLR4-dependent processes in platelets, stored in apheresis-derived platelet concentrates, will be analyzed. The aims of the project are: 1) to characterize the extent of known TLR2- or TLR4-dependent effects like intracellular ROS (reactive oxygen species) production or ligand-uptake in platelets with different storage time and storage temperature; 2) to explore further potential TLR-associated effector mechanisms (e.g. specific ROS sources or platelet-leukocyte interactions); to identify molecular interaction partners of TLR2 and TLR, regulating the responsiveness of receptors depending on storage time and storage temperature. The results will contribute to the understanding of immunological mechanisms in stored platelets and provide novel ideas for the optimization of storage strategies.

• DFG Programme: Research Grants