Quantitative Changes of T Helper Cell 3 and CD4⁺CD25⁺T Regulator Cells in Peripheral Blood and the Serum Levels of TGF-β1 of the Patients with Severe Aplastic Anemia.

Objective To probe the mechanism of autoimmune intolerance in severe aplastic anemia (SAA), the percentages of Th3 cells and CD4⁺CD25⁺T regulator cells in peripheral blood and the serum levels of TGF-β1 of SAA patients at disease active and recovery phases and those of normal controls were measured.

Methods By FACS, the quantity of TGF-β producing CD4⁺ T cells (Th3)in the peripheral blood of 20 patients with SAA at active phase,10 patients with SAA at recovery phase and 12 normal controls were detected respectively. By FACS, the percentages of CD4⁺CD25⁺T regulator cells in peripheral blood of 12 patients with SAA at active phase, 9 non-recuperated patients after IST, 6 patients at recovery phase and 12 normal controls were counted, and its correlation with the percentages of CD3⁺CD4⁺, CD3⁺CD8⁺ cells and the ratio of CD3⁺CD4⁺to CD3⁺CD8⁺ were analyzed. By enzyme linked immunosorbent assay (ELISA), the level of TGF-β1 in serum of 25 patients with SAA and 13 normal controls were measured respectively and its correlation with peripheral platelets counts was analyzed.

Results The percentages of Th3 cells, CD8⁺TGF-β1⁺cells and the ratio of Th3/CD8⁺TGF-β1⁺in peripheral blood of controls were(5.10±3.16)%,(4.93±3.36)%,1.20±0.67 respectively, and those of the patients with SAA at active phase were(1.33±0.91)%,(1.72±1.07)%,1.00±1.13 respectively. Th3 cells and CD8⁺TGF-β1⁺of SAA patients were significantly lower than those of normal controls(p<0.01, p<0.05). The aforementioned merits of SAA patients at recovery phase increased to(2.19±0.66)%,(2.07±1.03)%,1.71±1.64 respectively, but the percentages of Th3 cells and CD8⁺TGF-β1⁺were still significant lower than those of normal controls (P<0.05). The percentage of Th3 cells decreased in the SAA patients, which broke the autoimmune tolerance in SAA. The percentage of CD4⁺CD25⁺T regulator cells in peripheral blood of controls was(8.25±6.78)%, and that of SAA patients was (3.32±2.80)%, which was significantly lower than that of normal controls. The percentages of CD4⁺CD25⁺T regulator cells of 9 non-recuperated patients and 10 patients at recovery phase increased to(7.09±5.52)% and(7.49±4.03)% respectively, which were not significantly different from those of normal controls. The percentage of CD4⁺CD25⁺T regulator cells of SAA patients was related to the percentage of CD3⁺CD4⁺ cells and the ratio of CD3⁺CD4⁺and CD3⁺CD8⁺ positively, but related to the percentage of CD3⁺CD8⁺cells negatively. The percentage of CD4⁺CD25⁺T regulate cells decreased in the SAA patients, which broke the autoimmune tolerance in SAA. The level of TGF-β1 in plasma of normal controls was (11.06±1.75) ng/ml. That of SAA patients was (2.49±2.55) ng/ml, which was markedly lower than that of normal controls(p<0.001). The level of TGF-β1 in plasma of SAA patients was related to the percentage of Th3 cells and the platelet counts positively (p<0.05, p<0.001). The level of TGF-β1 in the plasma of SAA patients decreased.

Conclusion The percentages of Th3 and CD4⁺CD25⁺T regulate cells in the peripheral blood, and the level of TGF-β1 in plasma of the SAA patients decreased, which broke the autoimmune tolerance in SAA.