The Accuracy of Extended Histopathology to Detect Immunotoxic Chemicals

The accuracy of extended histopathology to detect immunotoxic chemicals in female B6C3F1micewas evaluated under the auspices of the National Toxicology Program (NTP). A workgroup was formed consisting of four pathologists who conducted extended histopathological evaluation of lymphoid tissues obtained from a subset of NTP toxicology studies, in which previously detailed immunotoxicity assessment was performed. In addition, a positive control data set of three known immunosuppressive agents, one negative control data set, and an additional negative control group composed of the vehicle only treated groups were included. Data obtained fromextended histopathology evaluationswere com-pared to more traditional immune test results (both functional and nonfunctional) from previously conducted immunotoxicity assess-ments. Analyses of the data indicated that the ability to identify immunotoxic chemicals using histological endpoints decreased lin