Alteration of immune function following dietary mycotoxin exposure.
Mycotoxins are a group of structurally diverse fungal secondary metabolites that elicit a wide spectrum of toxicologic effects. Of particular interest is the capacity of some mycotoxins to alter normal immune function when present in foods at levels below observable overt toxicity. Aflatoxin, patulin, citrinin, and zearalenone experimentally alter immunity, and recent evidence suggests that the immunologic effects of ochratoxin A and trichothecenes may have particular significance to human and animal health. For example, the capacity of ochratoxin A to inhibit natural killer cell activity and increase growth of transplantable tumour cells has been associated with renal and hepatic carcinomas in mice and might similarly contribute to human cancer. Impaired resistance to pathogenic microorganisms occurs after exposure to the trichothecenes T-2 toxin and vomitoxin. This may predispose food animals to infectious disease and could result in decreased productivity as well as increased animal-to-human transmission of pathogens such as Salmonella and Listeria. Vomitoxin also alters normal mucosal immune function, specifically at the level of regulation of development, differentiation, and homing of IgA-producing plasma cells. Interestingly, vomitoxin-induced enhancement of IgA production in the systemic compartment contributes to manifestations in the mouse that are highly analogous to human IgA nephropathy, the most common form of human glomerulonephritis worldwide. Over the long term, the extrapolation of mycotoxin-induced immunologic effects observed in inbred mice to actual disease in livestock and humans will require investigations that both simulate natural exposure conditions as well as improve understanding of the cellular and molecular bases for these effects among different species.