OECD Series on Adverse Outcome Pathways

An Adverse Outcome Pathway (AOP) describes a logical sequence of causally linked events at different levels of biological organisation, which follows exposure to a stressor and leads to an adverse health effect in humans or wildlife. AOPs are the central element of a toxicological knowledge framework, promoted by member countries through OECD, built to support chemical risk assessment based on mechanistic reasoning. These AOPs are available in the AOP-Wiki, an interactive and virtual encyclopaedia for AOP development. Following their development and review, the endorsed AOPs are published in the OECD Series on Adverse Outcome Pathways. As scientific knowledge progresses, the publication of an AOP in this series does not preclude regular updates or new contributions to a given AOP. While the AOP-Wiki is a dynamic tool, only impactful changes to the AOP will be reflected in subsequent updates of the published AOP.


Adverse Outcome Pathway on inhibition of calcineurin activity leading to impaired T-cell dependent antibody response

The present AOP describes the inhibition of calcineurin activity resulting in impaired T-Cell Dependent Antibody Response (TDAR). Calcineurin (CN), a protein phosphatase, is known to impair immune function when its phosphatase activation is inhibited. CN inhibitors (CNIs) inhibit CN phosphatase activity to suppress many kinds of immune functions and have been used in the medical domain to prevent hyper immune reactions. However, CNIs are reported to also induce immunosuppression-derived adverse effects such as increased frequency and/or severity of infections and increased tumor incidences. CNIs might affect several T-cell derived immune functions to induce compromised host. Among the affected immune functions, T-cell dependent antibody response (TDAR) is an important factor to resist infections and thought to be the useful endpoint on evaluating immunotoxicity of chemicals; therefore, this AOP describes the linkage between the inhibition of CN activity and impairment of TDAR.


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