Specific antibody responses of primary cells from different cell sources are able to predict immunotoxicity in vitro.

Alternative methods for the prediction of immunotoxicity are highly desirable. However, until now no in vitro test for this purpose has been fully validated or accepted by regulatory authorities. MD cultures are in vitro equivalent to the widely used ex vivo primary T cell dependent antibody responses (TDAR), which has been identified in a regulatory context as a main functional test for immunotoxicological investigations. The purpose of the present study was to use MD cultures of spleen and blood cells to compare data from three different chemicals using SRBC as antigen in two different species. Using this approach we were able to show that cell sources from both rats and mice were able to correctly predict all tested compounds and to clearly distinguish immunosuppressants from control substances. Furthermore, animal studies can be refined by using MD cultures of PBMC. During a 28 d benzo(a)pyrene treatment of rats we were able to follow the kinetic of an immune response by in vitro analyses. Additionally evaluation of in vitro antibody responses of spleen cells and PBMC from rats treated with cyclophosphamide revealed similar results compared to the conventional ex vivo plaque forming cell assay (PFCA). In conclusion, investigation of in vitro antibody responses is a sensitive and reliable approach for detection of a compound induced specific effect on the immune system. MD cultures may not only replace the ex vivo TDAR in the future, but their implementation in routine toxicology also enables refinement of existing in vivo studies by reducing the numbers of animals.