A well-functioning immune system is essential for maintaining the integrity of an organism. Immune cells are an integral part of other systems including the respiratory, dermal, gastrointestinal, neurological, cardiovascular, reproductive, hepatic, musculoskeletal system, and endocrine systems. As a consequence, exposure to immunotoxic compounds can have serious adverse health consequences affecting responses to both communicable and non-communicable diseases. It is therefore important to understand the immunotoxic potential of xenobiotics and the risk they pose to humans.
Developing novel test methods to evaluating the immunotoxic potential of xenobiotics, Japan has developed five Adverse Outcome Pathways (AOPs) for immunotoxicity in the Organisation for Economic Co-operation and Development (OECD) project.  Based on the AOPs, Japan is on-going a Detailed Review Paper (DRP) for In vitro tests addressing immunotoxicity with a focus on immunosuppression. The DRP aims to present and discuss the application and interpretation of in vitro immunotoxicity assays, mainly covering immunosuppression, and to define a tiered approach to testing and assessment. 　After accepting the above documents, Japan is planning to develop test guidelines for in vitro immunotoxicity to OECD.