Chronic Ethanol Exposure Alters Leukocyte Subsets in Repopulating Spleens, But Does Not Alter Negative Selection in Thymuses of Sublethally Irradiated Mice

Abstract

Results from previous in vitro experiments in this laboratory suggested that ethanol may affect selection processes in the thymus. To determine whether ethanol allows escape of potentially autoreactive T-cell clones from negative selection, we fed ethanol to sublethally irradiated, young, adult C57BR mice during the time of thymic and splenic repopulation as a new model of human third trimester fetal alcohol exposure. The mice received a whole-body, sublethal dose (6 Gy) of gamma irradiation at 5 to 6 weeks of age. Feeding of a liquid diet providing 25% of calories as ethanol (EDC) or an isocaloric control liquid diet was begun 3 days after irradiation and was continued for 5 weeks. Each EDC mouse had 2 weight- and age-matched controls, 1 pair-fed (PF), and 1 fed ad libitum (AD LIB). Average blood alcohol concentrations (90 to 440 mg/100 ml) were higher than those reported previously for neonatal mice exposed to ethanol through lactation. At 5 weeks after irradiation, the EDC mice had lower total thymocyte numbers (p < 0.05) and a higher proportion of CD4- CD8- thymocytes than either the PF or AD LIB mice (p < 0.05), which is consistent with findings using in utero models of ethanol exposure. Ethanol exposure also altered the proportion of leukocyte subsets in repopulating spleens. B cells were the most sensitive to the detrimental effects of ethanol and, as a percentage of total nucleated cells in the spleen, B cells were decreased in the EDC group, compared with both the PF and AD LIB groups (p < 0.05). C57BR mice normally delete by negative selection thymocytes bearing vβ17+ T-cell receptors. There was no discernible effect of ethanol exposure during thymic and splenic repopulation on the expression of Vβ17a on thymocytes and splenic T lymphocytes, indicating that ethanol does not affect negative selection.