SiteCELL enables <i>on-site</i> PBMCs purification and cryopreservation for immune single-cell profiling of underrepresented ancestries

Population-level immune single-cell profiling has the potential to enable the association of cellular function with human ancestry, demographic, and environmental variables. However, methods for collecting and processing peripheral blood mononuclear cells (PBMCs) for single-cell sequencing are difficult to implement in remote and rural settings, resulting in a lack of representation of underserved communities across the global south. We developed SiteCELL, a method that enables purification and cryopreservation of PBMCs from whole blood at the site of collection using minimal laboratory equipment and without electricity. By comparing matched samples of purified PBMCs, we showed that SiteCELL performs as well as ficoll density gradient (FDG), both in laboratory and rural settings. This method ensures accurate recovery of cell type proportions and excels in reducing stress and minimizing variability in sampling batches across countries. Hence, SiteCELL is ideal for multinational initiatives targeting the inclusion of underrepresented ancestries in cellular atlases.