Peripheral Blood Mononuclear Cells (PBMCs) derived from whole blood or leukapheresis are the ideal starting material for isolating T cells, B cells, natural killer cells, and monocytes. The term “fresh PBMCs” is often used to refer to samples that were collected within 24 hours of use, and many researchers are adamant that fresh PBMCs consistently provide optimal results. However, the decision between fresh or frozen primary cells may not be so straightforward: factors such as cell type, cell functionality and logistical flexibility should be considered when selecting a format.
We spent several months researching this issue and evaluated both fresh and cryopreserved formats based on cell viability, logistical requirements and product consistency. The results demonstrated that fresh and cryopreserved PBMCs are surprisingly similar across most evaluation areas, but may offer distinct advantages over one another depending on the research application.
Evaluation Area #1: Cell Viability
Cell viability and recall response can be measured using flow cytometry and recall antigen assays testing cytokine secretion.(1) When samples are measured in their fresh state and post-thaw state following 1 week of cyropreservation, it is clear that fresh cells slightly outperform cryopreserved in terms of cell viability. However, when analyzing cell types that comprise significant portions of the leukocyte population, such as CD3+ T cells or monocytes, a small decline in viability due to the freeze/thaw procedure does not impact these more robust populations due to their high number as compared to rare cell populations. In fact, Pan T Cell products have higher viability in the in the cryopreserved format (following thaw) than fresh Pan T Cell products that were tested 24 hours from collection.
Average Cell Viability %
When it comes to PBMC products, it is important to understand the length of time between collection and cryopreservation. If transit time to the lab is more than 24 hours, then fresh cells begin to decline in viability and cryopreserved products are a better choice. Cytologics offers both fresh and cryopreserved PBMCs that are isolated and shipped (or cryopreserved) on the same day as collection, typically within 4 hours of arriving at our lab. With our PBMC products, you never have to worry about viability. For fresh PBMCs, we rigorously control our collection, processing and shipment timeline to fit your needs and ensure optimal viability. Cryopreserved products are shipped on dry ice at about –80°C to maintain a consistent temperature and high viability.
Evaluation Area #2: Procurement Speed
A major drawback of sourcing fresh PBMCs is the coordination of collection and experimental schedules. The logistical coordination required for fresh products is more costly and time consuming than cryopreserved products. Cyropreserved PBMCs can be held in inventory for several weeks and are readily available for shipment. Therefore, cyropreserved PBMCs are more favorable than fresh PBMCs in terms of procurement speed. At Cytologics, we can typically fulfill an order for cryopreserved PBMCs within 1-2 days whereas fresh PBMCs may take 1-2 weeks.
Evaluation Area #2: Product Consistency
As with many biological investigations, it is often desirable to perform batch analyses of immune cell responses on stored samples. This requirement stems from logistic considerations and from a need to reduce interassay variations, especially when samples are collected longitudinally from the same subjects. Cryopreserved cells offer the opportunity to purchase large lots from the same donor, which eliminates donor-to-donor variability. In addition. the cellular function of viable cells can be influenced by the presence of dead or dying cells, which are more common in fresh products once 24 hours have elapsed since collection.(2) When measuring cell populations for consistent function, we found that cryopreserved products thawed correctly assure the highest consistency.
At Cytologics, our mission is to provide you with high quality cells to support your research objectives. We offer a wide array of PBMCs and primary cells derived from peripheral blood and our quality management system ensures the highest possible cell viability. We are here to assist you if you have any questions regarding our fresh or cryopreserved cell products. Contact Us today!
References
(1) Smith et al. (2015). Intracellular Cytokine Staining and Flow Cytometry: Considerations for Application in Clinical Trials of Novel Tuberculosis Vaccines. PLoS One 10(9): e0138042.
(2) Synopsis of Cell Proliferation, Metabolic Status, and Cell Death. Cell Signaling Technology, 2020.
