A standard problem in cell preparations is limited purity and recovery, which causes variability in quality and potency of cell products. Highly pure populations can be obtained best using positive separation techniques. However, the latter are often based on high affinity antibodies whose usage causes unfavorable effects like strong and almost irreversible binding to cells, cell stimulation as well as receptor blockade. IBA’s Strep-tag®/Strep-Tactin® system is the platform for the novel traceless affinity cell selection (Fab-TACS®) of cells. Thereby, Fab-TACS® positive separation completely resigns the use of high affinity antibodies and ferromagnetic beads. In contrast, Fab-TACS® uses an immune-affinity chromatography based on Strep-tagged Fab-fragments (Fab-Streps) for reversible capture and release of target cells.

In more detail, a Strep-Tactin® coated matrix made of cell-grade agarose specifically binds low affinity Fab fragments. However, multiple Fab-Streps on IBA’s unique agarose bind target cells with high avidity. Hence, if a single-cell suspension passes through the agarose matrix target cells adhere to the matrix based on the exclusive binding of the Fab-Strep to the target cell. Non-target cells are efficiently washed away. In a final step, the addition of biotin causes the elution of the target cells and the Fab-Streps spontaneously self-dissociate from the cell surfaces due to their reduced affinity.
Thus, the innovative Fab-TACS® procedure delivers label-free, non-activated target cells in a standardized manner of highly reproducible quality from a variety of single cell suspensions, e.g. whole blood or buffy coat allowing a multitude of downstream applications.