Leukapheresis Procedure and Removing White Blood Cells from Leukopaks

Apheresis is a medical procedure in which a laboratory apparatus separates specific contents from a patient’s blood before returning the remaining blood to the patient.Through this process, plasma, red blood cells, platelets, or white blood cells can be removed from a donor, while the rest of the donor’s blood cells return to circulation in their body.

Various apheresis procedures are also employed to analyze and treat pathology. For example, diseased plasma, red (RBCs) or white blood cells (WBCs), or platelets can be removed from a patient’s circulating blood via apheresis. Apheresis procedures allow doctors to both remove elements of a patient’s circulating blood that are causing symptoms of disease, as well as study the pathology within the diseased blood constituents.

What is Leukapheresis?

Leukapheresis describes apheresis procedures that specifically remove leukocytes or peripheral blood stem cells from a patient’s blood sample.

How Does Leukapheresis Work?

Leukapheresis is typically conducted by running a patient’s blood through a leukapheresis machine, which arranges the different constituents of the sample into layers within the sample based on their density. These separate layers can then be removed from the sample independently of each other, to be studied or re-introduced to the patient’s bloodstream.

Leukapheresis Procedures in Medical Treatments

Leukapheresis has many promising applications in medicine. For example, leukapheresis CAR-T cell therapy first involves separating leukocytesfrom a patient’s blood via leukapheresis to obtain a sample containing a high concentration of leukocytes. The lymphocytes are then isolated from the other blood constituents, such as cells that inhibit T cell activation and proliferation. CAR genetic modifications can then be performed on these isolated lymphocytes, and the resulting CAR T cells are then cultured in the lab. Once the CAR T cells are ready to be re-introduced to the patient, the patient receives a CAR T cell infusion of their modified T cells and is monitored to ensure the patient’s body accepts the modified T cells.

Leukapheresis protocols can facilitate cancer research and oncological treatment. Lymphocytic leukemia patients have high numbers of leukemia cells circulating in their blood, which can cause dangerous cardiac and respiratory issues. While traditional chemotherapy can help reduce the number of leukemia cells in a patient’s blood, chemo procedures take several days to take effect and can be harmful to many organ systems within the body. In contrast, leukapheresis offers an immediate leukemia treatment option by directly removing the WBCs, including the leukemia cells, from a patient. That said, while leukapheresis can quickly lower the count of leukemia cells in a patient’s blood, chemo or monoclonal antibody treatments are still necessary to kill the cancer cells before the leukemia cell count rises again. However, this post-leukapheresis treatment allows for reduced doses of these therapies, which in turn reduces the instance of harmful side effects.

What are Leukopaks?

 Leukocytes removed from a patient during leukapheresis are gathered into a collection bag called a leukopak. A leukopak contains a high concentration of leukocytes that can be used in many downstream applications including transfusions or donations, to study pathology of the patient, or develop patient-specific treatments. Leukopaks are also a great starting material for scientists studying cell and gene therapy, vaccine development, or any large-scale project that would benefit from using a single donor. 

Leukopak vs Buffy Coat

 The term leukopak describes the highly concentrated sample of leukocytes removed from a patient’s blood during a leukapheresis protocol. Leukopaks contain leukocytes, RBC, at a significantly reduced concentration compared to whole blood, platelets, and granulocytes. A full leukopak can contain up to 20 billion leukocytes. 

A buffy coat specifically refers to the layer of WBCs and platelets that forms between the RBCs and plasma when a whole blood sample is centrifuged.Buffy coats contain lymphocytes, monocytes, granulocytes, and platelets, with the overall leukocyte population being ten to twenty times more highly concentrated in the buffy coat than in a whole blood sample.

The first decision a scientist must make when beginning an experiment is deciding on a starting material. Leukpaks and buffy coats both have the benefit of containing high concentrations of leukocytes compared to starting with whole blood. When choosing between a leukopak or a buffy coat a scientist should consider how many cells are necessary for their downstream applications. Since leukopaks are collected via leukapheresis they contain a much higher concentration of leukocytes from a single donor compared to buffy coats. Maintaining one donor throughout a set of experiments can eliminate donor-to-donor variability which can be advantageous. 

Leukopak Applications

Many pharmaceutics and healthcare companies produce and sell leukopaks to medical laboratories and therapeutics research facilities. Leukopaks can be analyzed for drug screening, cell therapy, and gene therapy, which require large numbers of white blood cells and peripheral blood stem cells to develop patient-specific therapeutics.

Leukopaks and Cell Separation

To study the characteristics of specific cell subsets in a leukopak or to develop a treatment for a specific leukocyte pathology, the cells of interest must be further separated from the other cell types within the leukopak. As with any biological sample, a variety of cell sorting, or cell separation protocols can be employed to isolate and collect specific cells for downstream analysis and therapeutics development.

While traditional cell sorting methods such as Fluorescence-Activated Cell Sorting (FACS) or Magnetic-Activated Cell Sorting (MACS) procedures can reliably isolate specific cells within a sample, these methods subject samples to high-energy environments or intense physical forces that pose risk to the health and viability of cell populations, and require an initial step to isolate PBMCs from a buffy coat or leukopak before isolating cells of interest. As such, subjecting a costly leukopak sample to FACS, MACS, or other common cell separation protocols could lead to lysing or damaging the target cells. Furthermore, these cell sorting methods typically involve expensive laboratory equipment and extensive, specialized training of lab personnel, which may prevent small labs and therapeutics startups from achieving efficient, effective workflows.

Sorting Leukopak Cells with Microbubbles

Akadeum Life Sciences offers an elegant solution to cell sorting that is affordable, simple, and preserves the health of cells in a sample. Buoyancy Activated Cell Sorting (BACSTM) with Akadeum’s microbubble kits relies only on the molecular affinity between biocompounds and the simple mechanism of buoyancy to process cell samples quickly and at scale. There is no need to isolate PMBCs from the leukopak prior to the T cell isolation.

How do the microbubbles work? First,  biotinylated antibodies are mixed into a biological sample and these antibodies bind with the unwanted cells present in the sample. Then, streptavidin-coated microbubbles are mixed into the solution—the streptavidin on the microbubbles binds with the biotin on the antibodies, allowing the microbubbles to effectively “capture” the unwanted cells in the sample. Then, the microbubbles and their unwanted cellular companions gently float to the surface of the sample for collection. What remains after isolation is a highly pure, highly viable sample of the desired cells ready for subsequent analysis.

With Akadeum’s BACS microbubble kits, specific cell types within a leukopak can be isolated with ease and accuracy. Check out Akadeum’s Microbubble Leukopak T Cell Isolation Kit to learn how cell sorting with microbubbles can improve your leukopak processing workflows.

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