Blood samples from healthy donors were obtained from the Blutspende Zürich blood donation center (Schlieren, Switzerland). The study was conducted in accordance with the principles of the Declaration of Helsinki, and the project was approved by the Swiss Association of Research Ethics Committees (BASEC-Nr: 2019-01721). Fresh samples were shipped in dry ice and kept at 4℃ for a maximum of 48 hours. Standard protocols for the fractionation of human whole blood were followed. A commercial density-gradient medium (Lymphoprep TM , STEMCELL) was used to isolate mononuclear cells. After adding it to whole blood, the solution was centrifuged at 800 g for 30 minutes. The obtained sample comprised a bottom layer of RBCs, a buffy coat consisting of suspended WBCs and PLTs, and a top layer of plasma, proteins, and PLTs. The efficacy of the fractionation protocol was verified by flow-cytometry (Figure ).