Small but mighty: how the MACS-technology based on nanosized superparamagnetic particles has helped to analyze the immune system within the last 20 years.

Today, magnetic cell sorting and flow cytometric cell sorting both are state-of-the-art technologies, with a plethora of applications in biology and biomedicine. Both technologies have their stand-alone applications, but they also perfectly complement each other, in particular for the analysis and isolation of fragile and rare cells. The technological evolution from simple magnets and steel wool separation columns to sophisticated instrumentation and automated procedures has paved the way for magnetic cell separation in the scientific community. This review will focus on applications of magnetic cell sorting with commercially available paramagnetic MACS(R)-nanoparticles (Miltenyi Biotech, Bergisch-Gladbach, Germany) that have allowed unprecedented approaches to the exploration of the immune system in basal and clinical research of humans and rodents. Thus, during the last 20 years this technology has been continuously developed so that the widest array of leukocyte subsets, stem cells, and connective tissue cells can be addressed by MACS(R)-conjugated antibodies directed against cell-specific surface antigens or secreted cytokines for research and clinical applications.