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In today's article, we have the privilege of delving into the world of Leukopaks.
Leukopaks are enriched leukapheresis* products—an ideal source of human primary cells when large numbers of cells are required from a single donor. Like whole blood and buffy coats, leukopaks typically contain various immune cells, including T cells, B cells, natural killer (NK) cells, monocytes, etc. However, compared to whole blood and buffy coat, a full-size leukopak contains much higher concentrations of leukocytes per volume—typically greater than 9 billion cells in an average volume of < 200 mL. For a reference on the typical frequencies of each cell type in different cell sources, including leukopaks, whole blood, and peripheral blood mononuclear cells (PBMCs), get your free copy of the Frequencies of Human Cell Types in Blood-Related Sources wallchart.
For researchers working on adoptive cell therapy, T cell receptor (TCR) sequencing, and immunotherapy development, leukopaks allow for scalability, consistent cell composition, and reproducibility of experiments since they provide large numbers of cells sourced from a single donor. Compared to other cell sources, such as whole blood and PBMCs, leukopaks also offer higher yields of different immune cell types, standardization, and flexibility in experiments due to long-term storage capabilities. To use leukopaks efficiently for streamlining your experiments, choosing a trusted supplier of quality cells is crucial. It is also important to determine whether fresh or frozen leukopak products would be more appropriate for your application and to establish an efficient processing protocol/workflow that ensures high cell viability.
Figure 1. Mean percentages of cell subpopulations in a frozen leukopak
Representative chart showing the average frequencies of major immune subsets in leukopak products, as measured by flow cytometry before cryopreservation. Values shown are mean percentages of total viable leukocytes present in a frozen leukopak (n ≥ 30).
Leukopaks are generally available as fresh or frozen products. At STEMCELL, fresh or frozen leukopaks** are collected in transfer bags using stringent and consistent protocols and offered in full, half, quarter, and tenth sizes. Whether to use fresh or frozen leukopaks depends on the specific needs of your experiment, such as cell type and functionality, logistics, availability, and timing flexibility. Thus, choosing a supplier that ensures a reliable supply of cells, with maintained quality and viability throughout the collection and shipping process, is imperative to the success of your research.
Fresh leukopaks
Fresh leukopaks are typically used to study the functions of white blood cells within a short period of time after collection. This is because fresh leukopaks contain viable and functional white blood cells that can be used immediately after collection without any loss of viability or functionality. STEMCELL's recent stability study suggests that fresh leukopaks can be stored at 2 - 8°C for up to 5 days post-apheresis.
Frozen or cryopreserved leukopaks
Frozen leukopaks, as the name suggests, are leukopaks that are cryopreserved and stored at a subzero temperature (normally ≤ -135°C) to preserve the biological sample for long-term storage. At STEMCELL, frozen leukopaks are processed shortly after collection, following stringent protocols, and cryopreserved in CryoStor® CS10—preserving quality and ensuring optimal cell viability and purity post-thaw.
Figure 2. Factors to consider when choosing the right leukopak product for your research
Comparison of fresh or frozen leukopak product features to help you choose the ideal source of human primary cells for your downstream applications.
As with any human biological material, obtaining quality starting material and managing the inherent variability and changes in stability over time are important factors to consider before processing a leukopak for downstream cell isolation. Both fresh and frozen leukopaks can be further processed into their cellular components, such as PBMCs and other isolated immune cell subsets of interest. This process can be arduous and, if done incorrectly, could result in reduced cell viability, hindering downstream experiments. Thus, choosing the right protocol and tools to efficiently process a leukopak and achieve ideal cell isolation is essential.
The following should be considered to ensure efficient leukopak processing:
STEMCELL Technologies offers various high-quality, ethically sourced human primary cells** and resources to meet your research needs. We can also accommodate your unique requirements with personalized service and customizable products, including products that meet specific isolation and anticoagulant requirements, custom cell isolation kits, cell culture media, and more. To learn more, visit our Science Exchange storefront.
*Leukapheresis is a process of collecting white blood cells (WBCs) from peripheral blood of a healthy donor and returning the remainder to the circulation.
**Certain products are only available in select territories.