The Expression of Retinoic Acid Receptors in Thymus of Young Children and the Effect of All-Transretinoic Acid on the Development of T Cells in Thymus

To explore the effect of retinoic acid on the development of T cells in thymus, we examined the expression and distribution of retinoic acid receptors mRNA in thymus of young children (≤5 years of age) and investigated the affection of all-transretinoic acid on the differentiation and maturation of the T cells in thymus and cultured in vitro. Twenty thymus samples were collected. By in situ hybridization, we found that four retinoic acid receptor genes expressed in thymus, and the levels of mRNA for retinoic acid receptor genes (detected by reverse transcriptase, fluorescent quantitative PCR), were changed with age. In in vitro culture, all-transretinoic acid promoted the maturation from CD4+CD8+ cells to CD4+ cells but inhibited the differentiation from CD4+CD8+ cells to CD8+ cells. Thus, retinoic acid likely plays important roles in T cell development in thymus and perhaps by affecting the relative expression of retinoic acid receptors.