Both fresh and frozen leukopaks are ideal starting materials for downstream cell isolation when large numbers of cells are required, reducing the time and reagents needed to process cells of interest. A couple of key considerations for deciding between using fresh or frozen leukopaks for your experiments are highlighted below: Experiment start date: Frozen leukopaks offer more flexibility on when you start your experiments. If needed, they may be stored at -135ºC or colder until you are ready to process the cells. In contrast, fresh leukopaks should be processed upon receipt for best results. If absolutely necessary, they may be stored at refrigeration temperature (2 - 8ºC) until you are ready to process the product; however, there is expected cell loss with extended storage after receipt. For data on this, please see Data and Publications on the product landing page. Downstream use of cells: Cells isolated from a frozen leukopak may be used for a variety of assays after thawing. However, it is not advised to re-cryopreserve and bank cells isolated from a frozen leukopak for later use. Cells tend to be sensitive post-thaw and a second freeze-thaw cycle typically results in high cell death. Fresh leukopaks, in contrast, are ideal for either immediate use or cryopreservation (banking) of isolated cell types for later experiments.