To investigate the expression and significance of T cell count, BCL- 2 and BAX protein in patients with severe aplastic anemia after allogeneic hematopoietic stem cell transplantation.

From January 2014 to January 2018, 52 patients with severe aplastic anemia treated by allogeneic hematopoietic stem cell transplantation in our hospital were selected as the research objects. According to whether infection occurred after stem cell transplantation, they were divided into a non-infection group (32 cases) and an infected group (20 cases). The peripheral blood total T lymphocyte count (CD3⁺), T-helper/induced cell subsets (CD4⁺), T-suppressor/ toxic cell subsets (CD8⁺) and T-helper/T-suppressor cell ratio (CD4⁺/ CD8⁺) were detected by flow cytometry. The expression of BCL-2 and BAX protein was detected by enzyme- linked immunosorbent assay (ELISA). Two groups of patients were followed up for one year, and the survival of the two groups was recorded.

The levels of CD3⁺ (79.09±15.40), CD4⁺ (128.78±24.36), CD4⁺/ CD8⁺ (1.68±0.15) in the non-infected group were higher than those in the infected group CD3⁺ (57.62±10.36), CD4⁺ (86.17±11.22), CD4⁺/CD8⁺ (1.15±0.10). The levels of CD8⁺ (74.17±5.48) in the non-infected group were lower than those in the infected group (76.79±4.36). The difference was statistically significant (P < 0.05). The levels of BCL- 2 (0.48±0.10) eggs and BCL-2/BAX (1.07±0.06) in the non-infected group were higher than those in the infected group (0.34±0.07) eggs and BCL-2/BAX (0.83+0.04). The level of BAX (0.33±0.04) in the non-infected group was lower than that in the infected group (0.41±0.12). The difference was statistically significant (P < 0.05). Pearson correlation test showed that CD4⁺/ CD8⁺ was positively correlated with BCL-2/ BAX in patients with severe aplastic anemia after allogeneic hematopoietic stem cell transplantation (r = 0.620, P < 0.001). The 1-year survival rate of the non- infected group was 90.63% (29/32) and that of the infected group was 50.00% (10/20). There was significant difference between the two groups (χ² = 6.2184, P = 0.0064) .

Infection after allogeneic hematopoietic stem cell transplantation in severe aplastic anemia may lead to abnormal immune function, which may be related to the up-regulation of apoptotic protein BCL-2 expression. Infection after stem cell transplantation significantly shortens the survival time of patients.