Abstract: Objective: To investigate the proportion of regulatory T cells(Treg cells) in peripheral blood and the expression of programmed death receptor-1 (PD-1) on Treg cells in adult primary immune thrombocytopenia(ITP) patients, and to analyze their clinical significance. Methods: Altogether 30 patients with ITP were enrolled and divided into effective group（21 patients）and ineffective group（9 patients）according to whether platelets returned to normal level after treatment. Flow cytometry(FCM) was applied to determine the counts of CD3⁺ T lymphocytes, and proportions of Treg cells and PD-1⁺ Tregcells in ITP patients pre- and post-treatment. Results: The count of CD3⁺ T lymphocytes was not differed significantly before and after treatment in both the effective treatment group [6.39±5.74)×10⁹/L vs (5.49±4.86)×10⁹/L] and ineffective group[(8.34±2.95)×10⁹/L vs (7.87±1.47)×10⁹/L]. The proportion of Treg cells increased from 16.96%±4.61% to 32.74%±9.38% in effective treatment group(P<0.05), and the proportion of PD-1⁺ Treg cells increased from 14.88%±6.75% to 29.62%±7.97%(P<0.05). In contrast, Treg cells increased a little and maintained at a low level in ineffective group (from 17.41%±6.77% to 19.18%±7.64%, P>0.05) and PD-1⁺ Treg had no significant increase (from 15.30%±6.57% to 19.58%±6.91%, P>0.05). Moreover, the proportions of peripheral blood Treg cells and PD-1⁺ Treg cells in the effective group were significantly higher than those in the ineffective group after treatment (P<0.05). Conclusions: Treg cells and PD-1⁺ Treg cells may play an important role in the development and progress of ITP. The detection of proportion of these two cells in peripheral blood might be helpful to predict the prognosis of ITP.

Key words: Immune thrombocytopenia, Primary, Regulatory T cells, Programmed death receptor-1