Cell isolation

Cells serve as an important research tool to investigate different mechanisms in health and disease. They are also suitable for diagnostic and therapeutic purposes, making them attractive for a broad area of research fields. Immune cells have a wide range of functions such as controlling body homeostasis, which includes elimination of infected or cancerous tissue. Therefore, these cells are frequently employed for different analyses and model systems. The advantage of using immune cells is that they are abundant in, for example, human blood or mouse spleen, two sources that are relatively easily accessible for research purposes.

The interaction of cells with each other is very complex and for some experimental setups it is necessary to isolate one specific population for further downstream applications and analyses. Those include for example DNA/RNA isolation, single cell RNA sequencing, protein purification, Western blot or various cell culture experiments.

Immune cells commonly found in human blood.

Specific cells are most frequently isolated by targeting their surface markers or according to their antigen-specificity. For surface marker-specific cell isolation, generally one of these two approaches is used: positive or negative cell selection. Antigen-specific cell isolation usually requires a positive cell selection approach.

In positive selection, the target cells are directly labelled with for example antibodies conjugated to magnetic beads or fluorophores. The cells can subsequently be isolated using a magnet (magnetic-activated cell sorting – MACS) or a flow cytometer suitable for fluorescence-activated cell sorting (FACS).

Antibodies used for the positive cell selection approaches usually have a high affinity. This can cause unfavourable effects such as strong and almost irreversible binding to cells, cell stimulation (activation) as well as receptor blockade. In addition, magnetic beads often remain attached to the cells. Irreversible binding reagents can impair downstream applications due to a possible negative effect on cell functionality.

To avoid adverse effects of high affinity antibodies, Traceless Affinity Cell Selection (Fab-TACS^®/Nano-TACS^®) is the method of choice. This approach is based on our Strep-tag^® technology and uses low affinity Fab-fragments or nanobodies (Fab-Streps/Nano-Streps) instead of high affinity antibodies. It is possible to choose between affinity chromatographic, magnetic and fluorescent isolation methods depending on the Strep-Tactin^® backbone (Strep-Tactin^® TACS Agarose columns, Strep-Tactin^® Magnetic Microbeads or Strep-Tactin^® PE/APC) and is therefore adaptable to different experimental requirements. All isolation methods result into completely label-free cells after the isolation.