AUTHOR=Johnson Victor J. , Luster Michael I. , Maier Andrew , Boles Corey , Miller Eric W. , Arrieta Daniel E. TITLE=Application and interpretation of immunophenotyping data in safety and risk assessment JOURNAL=Frontiers in Toxicology VOLUME=Volume 6 - 2024 YEAR=2024 URL=https://www.frontiersin.org/journals/toxicology/articles/10.3389/ftox.2024.1409365 DOI=10.3389/ftox.2024.1409365 ISSN=2673-3080 ABSTRACT=The use of immunophenotyping during immunotoxicity investigations was first popularized in the 1980 s and has since become more integrated into diagnostic and non-clinical assessments. The data provided from immunophenotyping can serve as an initial source of information to guide decisions for additional, more advanced, immunotoxicity testing as well as for human health safety and risk assessment of drugs and chemicals. However, comprehensive guidance describing applications of immunophenotyping data in immunotoxicity investigations is lacking, particularly among regulatory bodies. Therefore, a critical examination is needed for the appropriate interpretations and potential misinterpretations of such data during the assessment of drug safety and chemical risk. As such, the current uses and implications of immunophenotyping data in human health safety and risk assessments has been evaluated to provide additional context for the application of current methodologies and guidelines. In addition, case studies are presented to highlight the challenges of interpreting immunophenotyping results along with incorporating the findings into immunotoxicity investigations. Based on the analyses of current approaches and methodologies, a decision flow is presented for use of immunophenotyping data during risk informed decision making.