Flow and image cytometry side by side for the new frontiers in quantitative single‐cell analysis

THE role of regulatory (CD4CD25) T-cells (Tregs) as therapeutics to replace common anti-inflammatory drugs is of increasing interest since cell therapy seems to be within reach (1). Practical aspects of purification and propagation of Tregs is now summarized by Trzonkowski et al. in the present issue (2). The authors demonstrate that novel advances in flow cytometry and also cellular immunology opens the door for the clinical application of Tregs. Affordable diagnostic tools for HIV and AIDS are of imminent importance in resource poor countries (3). To this end, PCR (4) and cell-based analysis (i.e. CD4 counting) by flow cytometry (5,6) or automated microscopic cytometry (7) is often the method of choice. The current PCR assays, however, often fail to detect virus variants that are prevalent in the third world. Thereby, these patients, despite clinical symptoms, may be diagnosed as virus negative and will not receive therapy. Now, Greve et al. present a new microparticle-based PCR assay that enables detection and quantification of HIV-1 viral load for most of the common variants including outlier, nonmajor, and circulating recombinant forms (8, commentary in 9). Malaria is also one of the great killers that needs appropriate diagnostic tools (7). Jimenez-Diaz et al. (10) developed an assay to quantify malaria-infected erythrocytes using the cell-permeable nuclear dye SYTO-16. The authors show the applicability of their assay for infected normal mice and human erythrocyte engrafted NOD mice. Because flow cytometers are now available in many resource poor settings, both assays can be introduced, relatively inexpensively. Finally, the research group of Edwards et al. applied a flow-cytometry-based high-throughput screening system (11) to identify novel formylpeptide receptor ligand probes. The authors screened more than 24,000 small molecules and finally came up with several candidates of potential future therapeutic or diagnostic interest (12,13). The aforementioned scientific articles of this issue illustrate that flow cytometry is still going strong with innovative technologies for versatile applications presented in our journal. However, every scientific journal has to evolve and adjust its focus to present and adjust for future requirements of the scientific community. In view of the increasing technological advances in imaging (14), our goal was to become a front journal for image cytometry and quantitative image analysis. As one can see from the citations in 2008 to Cytometry Part A, the readers find an increasing appreciation in our publications in the technological field of quantitative imaging. As one good example, Abella et al. (15) present an assay for automated quantification of cell infiltrates in histological sections based on microscopic images from allergic murine models. After extraction of texture parameters by a stepwise procedure the authors propose an algorithm that appears to be superior to manual cell counting. Yet another application is automated laser scanning cytometry (LSC) for mast cells tracking in skin as described by Zoog et al. (16). Rapid, accurate evaluation of mast cells present around wounds in a wound-healing model by automated LSC may serve as an important tool for tracking pharmacodynamic effects of MC-directed therapies. Without doubt we enter the era of automated cell detection in tissues (17). New labeling fluorescent tools for life-cell in vivo imaging are introduced by Robers et al. (18). High-affinity and selective ligand–receptor binding of 50-fluorescein-tagged synthetic ligand for FKBP12 (immunophilin) and mutated receptor