The SCID-hu mouse as a tool in immunotoxicological risk assessment: effects of 2-acetyl-4(5)-tetrahydroxybutyl-imidazole (THI) and di-n-butyltin dichloride (DBTC) on the human thymus in SCID-hu mice

SCID mice engrafted with human fetal thymus and liver tissue fragments (SCID-hu mice) are currently considered as a new tool in human immunotoxicological risk assessment. Testing of various immunotoxicants exerting thymotoxicity via different intrathymic target cell types is necessary for validation of this model. Therefore, SCID-hu mice were exposed to 2-acetyl-4(5)-(1,2,3,4-tetrahydroxybutyl)-imidazole (THI), the immunotoxic component in the food additive, Caramel Colour III, or the organotin compound, di-n-butyltin dichloride (DBTC). Histopathological examination of the human thymus grafts of SCID-hu mice either exposed to THI or to DBTC showed a reduction in the relative size of the thymus cortex, an effect also described in rodents. These results indicate that the human thymus is a target for the immunotoxic action of both THI and DBTC. In addition, they indicate the promising potential of the SCID-hu mouse model as a tool for human immunotoxicological risk assessment.