Current status of alternative methods for assessing immunotoxicity: A chemical industry perspective

Assessing Fish Immunotoxicity by Means of In Vitro Assays: Are We There Yet?

There is growing awareness that a range of environmental chemicals target the immune system of fish and may compromise the resistance towards infectious pathogens. Existing concepts to assess chemical hazards to fish, however, do not consider immunotoxicity. Over recent years, the application of in vitro assays for ecotoxicological hazard assessment has gained momentum, what leads to the question whether in vitro assays using piscine immune cells might be suitable to evaluate immunotoxic potentials of environmental chemicals to fish. In vitro systems using primary immune cells or immune cells lines have been established from a wide array of fish species and basically from all immune tissues, and in principal these assays should be able to detect chemical impacts on diverse immune functions. In fact, in vitro assays were found to be a valuable tool in investigating the mechanisms and modes of action through which environmental agents interfere with immune cell functions. However, at the current state of knowledge the usefulness of these assays for immunotoxicity screening in the context of chemical hazard assessment appears questionable. This is mainly due to a lack of assay standardization, and an insufficient knowledge of assay performance with respect to false positive or false negative signals for the different toxicant groups and different immune functions. Also the predictivity of the in vitro immunotoxicity assays for the in vivo immunotoxic response of fishes is uncertain. In conclusion, the currently available database is too limited to support the routine application of piscine in vitro assays as screening tool for assessing immunotoxic potentials of environmental chemicals to fish.

Exploring the use of current immunological assays for the developmental immunotoxicity assessment of food contact materials

The mammalian immune system is a highly complex, interactive network of cells that facilitates innate and adaptive immune responses. The neonatal immune system may be more susceptible to chemical perturbations than that of the adult. The effects of immunotoxicants during development may not be fully detected in toxicity studies performed on adult animals. Studies characterizing the ontogeny of the immune system in developing animals have shown that there are different critical windows of susceptibility to immunotoxicants. Developmental differences are evident among species compared to humans. Functional immune assays, such as the T-cell antibody dependent response assay, in rat models have been validated for use in the assessment of immunotoxicity with other assays. Recently, published studies have explored the feasibility of using additional techniques, such as in vitro studies using human whole blood cells or cell lines, mostly lacking either sensitivity or proper validation for regulatory purposes. However, some techniques may be developed further to enable translation of animal toxicity findings to human risk assessment of potential immunotoxicants. This paper summarizes the information on the developing immune system in humans versus rats and how the currently available assays might be used to contribute to the safety assessment of food contact substances.