In clinical research, the study of human peripheral blood mononuclear cells (PBMCs) plays a crucial role in advancing our understanding of the immune system and its responses. PBMCs are a heterogeneous population of white blood cells, including lymphocytes (T cells, B cells, and natural killer cells), monocytes, and dendritic cells. Isolating PBMCs from blood samples provides researchers valuable insight into immune cells and their responses. However, researchers' key decision is whether to use fresh or frozen PBMCs for their experiments. This blog explores factors to consider for each option to aid researchers in making informed decisions.
Definition of PBMCs & their importance in medical research
Peripheral blood mononuclear cells (PBMCs) are a diverse group of immune cells derived from the bone marrow's haematopoietic stem cells (HSCs) and are typically separated from peripheral whole blood samples. Comprising lymphocytes, monocytes, and dendritic cells, PBMCs are an essential part of our immune systems, which fight against pathogens and abnormal cells, comprising lymphocytes, monocytes, and dendritic cells. They participate in various immune responses, including antigen presentation, cytokine secretion, and cell-mediated cytotoxicity. PBMCs are pivotal in immunology, infectious disease research, haematological malignancies, vaccine development, and immunotherapy research, making them invaluable in advancing medical knowledge and therapeutic approaches.1
For research purposes, PBMCs can be fresh or frozen, and the choice between the two will largely depend on specific experimental requirements. There are advantages and disadvantages to using fresh and frozen PBMCs, but researchers should assess which option will be most suitable for their individual applications. In the following sections, we explore this topic further.
A quick guide to PBMCs
Fresh PBMCs offer several advantages for research purposes, including their ability to be used immediately with high viability and no concern of damage due to freeze-thaw. On the other hand, frozen PBMCs provide unique advantages, including increased storage options for researchers to process samples at their convenience rather than immediately upon receipt.
Optimal viability
Fresh PBMCs offer higher viability when the transit time from collection to the laboratory is shorter (less than 24 hours). Minimising the time between collection and processing helps maintain the cells' integrity and functionality – best practices suggest processing within eight hours. Therefore, minimising the time between collection and processing can help to preserve the cells' integrity and functionality, ideally completing processing within eight hours, according to best practices. When transit time from sample collection to laboratory exceeds 24 hours, the viability of fresh PBMCs can decline, which can compromise experimental outcomes. For this reason, some users located further from collection sites may opt for frozen PBMCs that aren't as heavily impacted by extended transit times.
Freeze-thaw processing
Freezing and thawing processes may reduce cell viability and functionality, leading to potential changes in cell composition. These processes can also reduce the number of innate cells present in frozen PBMC samples compared to fresh PBMCs. Researchers should use rate-controlled freezing and store samples in appropriate cryopreservation media to maintain post-thaw viability and minimise changes. It is essential to consider how these potential impacts may affect experimental outcomes and the interpretation of data.
Convenience in shipping & storage
Frozen PBMCs, processed shortly after blood draw and stored in appropriate cryopreservation media, are more convenient to handle, ship, and store than fresh PBMCs. They can be transported over long distances without compromising quality, offering flexibility to researchers far from sample collection sites.
Long-term storage
One of the critical benefits of frozen PBMCs is that they can be stored for long periods, allowing for future experiments and longitudinal studies. Suitable preservation techniques, such as cryopreservation media, can be implemented to maintain PBMC viability and functionality over time. Fresh PBMCs, meanwhile, have a limited shelf life and need to be processed promptly, meaning researchers must plan experiments accordingly to ensure the timely collection and processing of fresh PBMC samples.
Retention of phenotype & function
Even with the implications of freeze-thaw cycles, frozen PBMCs have been shown to retain their phenotype and functional characteristics . This enables researchers to study specific cell subsets and their immune responses effectively.
In summary, fresh PBMCs offer optimal cell count and viability benefits, making them suitable for immediate use in functional assays. It is worth noting that even with the implications of freeze-thaw processes, frozen PBMCs have been shown the retain their phenotype and functional characteristics, enabling researchers to study specific cell subsets and their immune responses effectively. It is important to note that freeze-thaw protocols should be optimised to minimise adverse effects on frozen PBMC quality, using rate-controlled freezing and appropriate cryopreservation storage media. Ultimately, fresh and frozen PBMCs have their use case depending on requirements and assay type, and the choice should align with the specific experimental needs and goals.
PBMCs with Cambridge Bioscience
We are an experienced provider of fresh and frozen PBMCs in partnership with Research Donors, a UK-based, HTA-licensed clinic specialising in collecting human blood biospecimens for research purposes. Our PBMCs are processed within 5 hours of blood collection to ensure high viability and minimal degradation. We are here to support your research with tailored collections for fresh PBMCs, or you can search our frozen PBMC inventory in real-time to select samples that meet your requirement.
References
- Hamot G, Ammerlaan W, Mathay C, Kofanova O, Betsou F. Method validation for automated isolation of viable peripheral blood mononuclear cells. Biopreserv Biobank. 2015 Jun;13(3):152-63. doi: 10.1089/bio.2014.0054. Epub 2015 Apr 1. PMID: 25830476.
- KofanovaOlga, A., DavisKristine, GlazerBarbara, SouzaYvonne, D., KesslerJoseph, & BetsouFotini (2014). Viable mononuclear cell stability study for implementation in a proficiency testing program: impact of shipment conditions. Biopreservation and Biobanking, 12, 206-216.
- Veluchamy JP, Delso-Vallejo M, Kok N, Bohme F, Seggewiss-Bernhardt R, van der Vliet HJ, de Gruijl TD, Huppert V, Spanholtz J. Standardized and flexible eight colour flow cytometry panels harmonized between different laboratories to study human NK cell phenotype and function. Sci Rep. 2017 Mar 10;7:43873. doi: 10.1038/srep43873. PMID: 28281564; PMCID: PMC5345017.
- Bull M, Lee D, Stucky J, et al. Defining blood processing parameters for optimal detection of cryopreserved antigen-specific responses for HIV vaccine trials. Journal of Immunological Methods. 2007. DOI: 10.1016/j.jim.2007.02.003
- Werner BA, McCarty PJ, Lane AL, Singh I, Karim MA, Rose S, Frye RE. Time dependent changes in the bioenergetics of peripheral blood mononuclear cells: processing time, collection tubes and cryopreservation effects. Am J Transl Res. 2022 Mar 15;14(3):1628-1639. PMID: 35422946; PMCID: PMC8991115.