[Abnormal expression of CXCR5+CD8+ T cells and CXCL13 in severe aplastic anemia patients and their correlation with hematological parameters].

Objective: To analyze the expression of C-X-C chemokine receptor 5 (CXCR5)+CD8+ T cells and plasma C-X-C motif chemokine 13 (CXCL13) in severe aplastic anemia (SAA) patients and their correlations with hematological parameters. Methods: The clinical data of 35 SAA patients in the Hematology Department of Tianjin Medical University General Hospital from January 2018 to September 2021 were retrospectively analyzed. The patients were divided into two groups according to whether they had received the medication: untreated SAA group and recovery SAA group. In untreated group, there were 18 patients who had not received any medication, with 9 males and 9 females, and aged 51 (18-76) years. In recovery SAA group, there were 17 patients who were separated from component blood transfusion after the immunosuppressive treatment with anti-thymocyte globulin (ATG) combined with cyclosporine A (CsA), with 7 males and 10 females, and aged 46 (16-70) years. Meanwhile, 20 healthy controls were also selected, including 8 males and 12 females, and aged 45(15-72) years. Peripheral blood and bone marrow samples were collected from SAA patients, while peripheral blood samples were obtained from healthy controls. Flow cytometry was used to detect the percentage of CXCR5+CD8+ T cells in peripheral blood and bone marrow samples. The concentration of plasma CXCL13 was measured by enzyme-linked immunosorbent assay (ELISA). The correlations between the percentage of CXCR5+CD8+ T cells and the concentration of CXCL13, as well as the correlations between these two parameters and the hematological parameters were analyzed by Spearman correlation analysis. Results: The proportion of CXCR5+CD8+ T cells in the bone marrow of untreated SAA group was (4.9±2.9)%, which was higher than that of recovery SAA group (2.7±1.5)%, with a statistically significant difference (t=2.34, P=0.027). The proportion of CXCR5+CD8+ T cells in peripheral blood of untreated SAA group, recovery SAA group and healthy control group was (8.4±4.2)%, (3.8±2.3)% and (2.6±2.0)% respectively. The proportion of CXCR5+CD8+ T cells in peripheral blood of untreated SAA group was higher than that of recovery SAA group and healthy control group (both P<0.05). The plasma CXCL13 concentration in untreated SAA group was (97.2±46.8) ng/L, which was significantly higher than that in recovery SAA group [(54.9±20.9) ng/L] and healthy control group [(47.6±17.3) ng/L] (both P<0.05). The proportion of CXCR5+CD8+ T cells in peripheral blood of SAA patients was positively correlated with the concentration of plasma CXCL13 (r=0.545, P<0.001). The proportion of peripheral blood CXCR5+CD8+ T cells in SAA patients was negatively correlated with white blood cell count, platelets count, percentage of neutrophils, absolute neutrophils count, percentage of reticulocytes, absolute reticulocytes count, bone marrow myeloid cells, bone marrow erythroid cells and megakaryocytes count (r=-0.556, -0.392, -0.617, -0.615, -0.395, -0.543, -0.432, -0.484 and -0.523, all P<0.05). The proportion of peripheral blood CXCR5+CD8+ T cells was positively correlated with the percentage of peripheral blood lymphocytes and bone marrow lymphoid cells (r=0.593 and 0.556, both P<0.05). Meanwhile, the concentration of plasma CXCL13 in SAA patients was negatively correlated with white blood cell count, absolute neutrophils count, percentage of reticulocytes, absolute reticulocytes count and bone marrow myeloid cells (r=-0.447, -0.446, -0.498, -0.407 and -0.456, all P<0.05), but positively correlated with bone marrow lymphoid cells (r=0.384, P<0.05). Conclusions: The proportion of CXCR5+CD8+ T cells and the concentration of plasma CXCL13 increases in SAA patients. The proportion of CXCR5+CD8+ T cells in peripheral blood is positively correlated with the concentration of CXCL13. Moreover, the proportion of CXCR5+CD8+ T cells and the concentration of CXCL13 are correlated with many hematological parameters, which may play a critical role in the immune pathogenesis of SAA.