Assessment of immunotoxicity in the 21st century: Where we are and what we need to replace animals.

The field of immunotoxicity assessment has traditionally relied on animal models, which have raised ethical concerns and presented limitations in terms of predictive accuracy and relevance to human health. This paper reviews the current state of immunotoxicity evaluation, emphasizing the importance of transitioning away from animal testing. Modern approaches, including in vitro methods, human-based studies, adverse outcome pathways (AOPs), and computational modeling, are discussed as viable alternatives. These non-animal methods offer enhanced predictive power and the potential for regulatory acceptance, though technical and practical challenges remain. Case studies demonstrate the success of non-animal methods, such as AOP-based assessments for skin sensitization and the pyrogen assay using whole blood cytokine assays. Despite these advances, further research is needed in areas like respiratory sensitization, developmental immunotoxicology (DIT), and microphysiological systems (MPS). Recommendations are provided to accelerate the adoption of new approach methodologies (NAMs), focusing on AOP frameworks. In conclusion, the paper highlights the key findings from current non-animal immunotoxicity research and issues a call to action for advancing these methods to improve safety assessment practices in the 21st century.