Thymocyte development in male fetal alcohol-exposed rats.

We previously reported altered responses of thymocytes to mitogen stimulation after fetal alcohol exposure (FAE) in prepubertal male Sprague-Dawley rats. The purpose of this study was to examine the effect of FAE on the developmental pattern of thymocyte subsets. In the first experiment, we found that the proportion of double-labeled CD4+CD8+ thymocytes is identical in fetal alcohol-exposed (E) and control (C) animals at 34 and 45 days of age. In the second experiment--at 20, 28, 35, and 48 days of age--we examined the proportion of CD4+ and CD8+ thymocytes that express or are devoid of the maturational markers, the alpha/beta configuration of the T-cell receptor (TcR), and the restriction fragment C of the common leukocyte antigen (CD45RC). We found significant age-dependent effects on the numbers of total double-positive CD4-TcR and CD8-TcR or CD45RC thymocytes, and significantly lower numbers of total CD4+ and CD8+ cells in E than in C rats throughout this period--a finding consistent with the significantly lower total number of thymocytes in E than in C rats. The developmental patterns for both markers were similar in E and C groups, in both the rising (days 20 to 28) and declining (days 35 to 48) phases. However, on day 35, E rats had significantly lower numbers of double-positive CD8-TcR and CD8-CD45RC cells than C rats. It therefore seems that FAE tends to accelerate the decline of double-positive CD8-TcR and CD8-CD45RC cells. The contribution of this phenotypic change to the thymic functional alterations induced by FAE remains to be determined.