The Leukapheresis Collection Process: How it works

It is natural, as a lab scientist, to value the access leukapheresis offers to high volumes of cells for your experiments all at the same time. Even if an entire leukopak isn't necessary or you work with cryopreserved PBMC, it is convenient to have a source of cells that is consistent and ready on the go.

Scientists often have a difficult time understanding how cells are collected through leukaphresis, but it is a worthy time investment in which to learn more about.

How Does Leukapheresis Work?

The principle of leukapheresis for collection of mononuclear cells (MNC) is separation by specific gravity.

Red blood cells have the highest specific gravity followed by granulocytes, then lymphocytes and monocytes, with platelets having the lowest density. During the leukapheresis procedure, whole blood is centrifuged to separate the cells and collect the cell type of interest.
Sounds easy, right? Of course, it isn’t that simple in practice.

Cell Separation

The separation of the cells is dependent on many factors, some of which can’t be controlled. The size of the donor’s veins is not going to change, for instance. Their blood pressure and heart rate can also have an impact.

The separation of blood fractions during leukapheresis, showing the three different cell layers and outlets for each layer. Source: Terumo BCT

The separation of blood fractions during leukapheresis, showing the three different cell layers and outlets for each layer. Source: Terumo BCT

Blood Volume

The donor’s total blood volume is a reflection of their body size, so it’s not surprising that a 220 lb man will have a greater blood volume than a 130 lb woman. The donor’s blood volume will also affect the amount of anticoagulant used. Because the anticoagulant is mixed with the blood as it enters the collection set, the ratio of anticoagulant to whole blood needs to be balanced. In practical terms, this means that the rate of separation will be faster for larger donors and slower for smaller donors.

Don’t expect 10 liters of blood volume to be processed from smaller donors. Only the big guys will be able to sustain the necessary flow rates.

Final Cell Product

Despite controlling for anticoagulant, cell packing, and fluids, there’s no predicting what the final makeup of the collection will be ahead of time. In theory, the collection of cells at a lower percentage of RBC (lower hematocrit) should result in a higher proportion of monocytes, but that degree of control is not possible.

Even when we keep all variables consistent, the results from one collection to the next may be different, even for collections from the same donor. All the more reason to appreciate the careful work of our apheresis staff!

Blog originally posted on Cellero.com