[Abnormal quantity of regulatory T cells in peripheral blood of patients with severe aplastic anemia and its clinical significance].

This study was purposed to investigate the role of regulatory T cells (Treg) in the immune unbalance for patients with acquired severe aplastic anemia (SAA). The flow cytometry was used to detect the quantity of CD4(+) CD25(+) CD127(dim) Tregs, T cell subset (CD4(+)/CD8(+) ratio), dendritic cell(DC) subset(mDC/pDC ratio) in 44 SAA patients(25 untreated patients and 19 recovery patients) and 23 normal controls. The correlation between Tregs and T cell subset, DC subset and hemogram were analyzed. The results showed that the percentage of CD4(+) CD25(+) CD127(dim) Tregs in peripheral blood lymphocyte(PBL) of untreated patients was (0.83 ± 0.44) %, which was obviously lower than that in recovery patients (2.91 ± 1.24)% and normal controls (2.18 ± 0.55)% (P < 0.05), but the difference was not statistically significant between latter two groups. The ratio of CD4(+)/CD8(+) was (0.5 ± 0.3) in untreated patients, which was obviously lower than that in recovery patients (1.2 ± 0.4) and normal controls (1.11 ± 0.24) (P < 0.05). The ratio of mDC/pDC was (3.08 ± 0.72) in untreated patients, which was significantly higher than that in recovery patients(1.61 ± 0.49) and normal controls (1.39 ± 0.36) (P < 0.05). The percentage of CD4(+) CD25(+)CD127(dim) Tregs in PBL positively correlated with CD4(+)/CD8(+) ratio (r = 0.695, P < 0.01), and that negatively correlated with mDC/pDC ratio (r = -0.796, P < 0.01). There were significant positive correlations between CD4(+)CD25(+)CD127(dim) Tregs/PBL and WBC, Ret% (r = 0.761, 0.749 respectively, P < 0.01). It is concluded that the decrease of CD4(+)CD25(+)CD127(dim) Tregs quantity in SAA may be one of mechanisms underlying bone marrow failure resulting from the deterioration of immune tolerance and hyperfunction of T-cells.