Flow cytometric and histological analysis of mouse thymus in fetal alcohol syndrome

Reduced thymus size and fetal weight were seen in 18-day old fetuses of C57BL/6 female mice fed a complete liquid diet containing 25% ethanol-derived calories (EDC) from gestational day 0 to 18. Thymocytes from fetuses from the 25% EDC diet group and from pair-fed and ad-lib control diet groups were compared by flow cytometry for expression of thymocyte differentiation antigens. The proportions of L3T4-positive and Lyt-2-positive thymus cells were significantly reduced in alcohol-exposed fetuses compared to controls; however, the number of Thy-l-positive cells did not differ among any of the groups. Histologically, the thymus from 25% EDC fetal mice failed to show the delineation between cortex and medulla that was seen in the thymuses of control fetuses. These results indicate that thymus immaturity is one of the accompanying features of fetal alcohol syndrome.