Detection and Significance of CD4+CD25+CD127dim Regulatory T Cells in Individuals with Severe Aplastic Anemia

OBJECTIVE: To investigate the relationship between CD4+CD25+CD127dim regulatory T cells (Tregs) and immune imbalance in acquired severe aplastic anemia (SAA). MATERIALS AND METHODS: The quantity of CD4+CD25+CD127dim Tregs in 44 SAA patients and 23 normal controls was measured by flow cytometry. Correlations between Tregs and T cell subsets, dendritic cell (DC) subsets, granulocyte counts, and percentage of reticulocytes (RET%) were analyzed. RESULTS: The percentage of CD4+CD25+CD127dim Tregs in peripheral blood lymphocytes (PBLs) of untreated patients was lower than in recovery patients and normal controls (0.83±0.44% vs. 2.91±1.24% and 2.18±0.55%, respectively, p<0.05). The percentage of CD4+CD25+CD127dim Tregs in CD4+ T lymphocytes of recovery patients was higher than that of untreated patients and normal controls (9.39±3.51% vs. 7.61±5.3% and 6.83±1.4%, respectively, p<0.05). The percentage of CD4+ T lymphocytes in PBLs of untreated patients was lower than in recovery patients and normal controls (13.55±7.37% vs. 31.82±8.43% and 32.12±5.88%, respectively, p<0.05). T cell subset (CD4+/CD8+ ratio) was 0.41±0.24 in untreated patients, which was lower than in recovery patients (1.2±0.4) and normal controls (1.11±0.23) (p<0.05). DC subset (myeloid DC/plasmacytoid DC ratio, DC1/DC2 ratio) was 3.08±0.72 in untreated patients, which was higher than in recovery patients (1.61±0.49) and normal controls (1.39±0.36) (p<0.05). The percentage of CD4+CD25+CD127dim Tregs in PBLs was positively associated with T cell subset (r=0.955, p<0.01) and negatively associated with DC subset (r=-0.765, p<0.01). There were significant positive correlations between CD4+CD25+CD127dim Tregs/PBL and granulocyte counts and RET% (r=0.739 and r=0.749, respectively, p<0.01). CONCLUSION: The decrease of CD4+CD25+CD127dim Tregs in SAA patients may cause excessive functioning of T lymphocytes and thus lead to hematopoiesis failure in SAA.