RESUMEN
<p><b>OBJECTIVE</b>To investigate the levels of CD4+CD25+CD127(low) regulatory T cells (Tregs) and the expression of Foxp3 gene in peripheral blood of children with aplastic anemia (AA) and to study their roles in the pathogenesis of AA.</p><p><b>METHODS</b>Twenty-one children with chronic AA, 9 with acute AA and 15 healthy children were enrolled. The proportion of CD4+CD25+ CD127low Tregs in CD4+ T cells was evaluated by flow cytometric analysis. The level of Foxp3 mRNA was ascertained by RT-PCR.</p><p><b>RESULTS</b>The percentage of peripheral blood CD4+T cells and CD4+CD25+ and CD4+CD25+CD127(low) Tregs in CD4+T cells in both the acute and chronic AA groups was significantly lower than that in the normal control group (P<0.05).The acute AA group had more decreased CD4+ T cells and CD4+CD25+ and CD4+CD25+CD127(low) Tregs percentage compared with the CAA group (P<0.05). The expression of Foxp3 mRNA in peripheral blood decreased obviously in the acute AA group (0.47 + or - 0.08%) compared with that in the normal control (0.71 + or - 0.12%) and the CAA groups (0.68 + or - 0.14%) (P<0.05).</p><p><b>CONCLUSIONS</b>The low expression of Tregs and Foxp3 mRNA in peripheral blood may be involved in pathogenesis of AA.The more decreased Tregs and Foxp3 mRNA expression in acute AA than chronic AA suggests their possible roles in the assessment of the severity of AA.</p>