Dear readers,

The last issue of 2021 of the European Journal of Immunology (EJI) is special in that it features, among other article types, the third edition of the ‘Guidelines for the use of flow cytometry and cell sorting in immunological studies’. Publishing this updated edition of the Guidelines should not be a surprise for the immunological community. As mentioned in our previous editorials [1, 2], EJI is one of the first journals recognised for its policy, which mandates that the flow cytometry data include the following information: (i) a full gating strategy, including the position of the positive and negative controls, (ii) the percentage of cells in the region/gate/event count, and statistics as appropriate, (iii) the marker (e.g. antigen), the fluorochrome/dye and (iv) the scaling (log/lin). These different experimental details are vital, because not only do they assure data quality, but they also help other researchers improve their presentation and design better experimental strategies. This format is particularly helpful for those researchers performing flow cytometry experiments on a given subset for the very first time. As such, our Guidelines represent an important resource to encourage best practices in flow cytometry across the wide immunological community.

The previous editions of the Guidelines [3, 4] have been very well received by the community, and are one of the most read articles in EJI. The Guidelines were spearheaded by Andreas Radbruch (EFIS president (2019–2021)), Andrea Cossarizza (President of the International Society for the Advancement of Cytometry (2020–2022)) and Hyun-Dong Chang (President of the German Society of Cytometry (2015–2016)), who helped define their specific features. Similar to the previous editions, the third edition of the Guidelines includes sections dedicated to detailed phenotype description and functional assays of all major human and murine cell subsets; however, this time functional assays are more comprehensively described. In addition, we include a Clinical relevance statement that highlights applications of flow cytometry to study human cells in clinical settings, with examples of flow cytometry analysis of various immune cell subsets in the context of autoimmune diseases, cancers and infections. To accommodate this substantial expansion of the clinical content, we have decided not include the content that was extensively covered in the previous versions such as the principles of flow cytometry and cell sorting, as well as advanced techniques in flow cytometry [4]. Instead, we have opted to create a focused handbook (still over 400 pages long!) that serves as a practical guide for every day laboratory use for both basic and clinical researchers.

The writing and preparation of this latest edition of the Guidelines took place during one of the most challenging period for our community, the pandemic caused by SARS-Cov-2, which disrupted all aspects of our personal and professional lives. We would like to express enormous gratitude to our collaborators, our authors as well as our referees, who tirelessly worked with us to help us improve the content and create a useful handbook for immunologists that is written by world leading immunologists and flow cytometry experts.

We hope you will find this version useful, and we would like to encourage you to send us feedback on this edition of the Guidelines and to drop an email to ejied@wiley.com if you have suggestions for additional Guideline topics.

Finally, we wish you a happier and healthier 2022, and we look forward to your precious feedback.