CD8+HLA-DR+ T Cells Are Increased in Patients with Severe Aplastic Anemia

To investigate the number and function of CD8+HLA-DR+ cells, which were considered to be activated CTL, in peripheral blood to further explore the pathogenesis of SAA.

The proportion of CD8+HLA-DR+T cells was analyzed by flow cytometry in peripheral blood of 38 SAA (26 untreated and 12 recovered) patients and 23 normal controls. Also the expression of perforin, granzyme B, TNF-β and FasL in CD8+HLA-DR+T cells was analyzed by flow cytometry and RT-PCR. Moreover, the apoptosis of CD3- bone marrow cells from normal persons after coculture with CD8+HLA-DR+T cells from untreated SAA patients was detected by staining with AnnexinV. The level of lactate dehydrogenase (LDH) in the supernatant were determined by automatic biochemistry analyzer.

The ratios of CD8+HLA-DR+T cells to CD8+T cells and to CD3+T cells were 39.3 ± 8.1% and 27.8±7.1% in SAA patients, and were significantly higher than the corresponding ratios in controls (18.3 ± 6.7% and 8.5 ± 2.3%) (P < 0.05). The expression values for perforin, granzyme B, TNF-β and FasL in CD8+HLA-DR+T cells in the untreated SAA group were 8.5%, 96.1%, 94.3% and 72.1%, respectively, which were higher than the corresponding values in the control group (1.8%, 82.0%, 32.9%, 15.6%). The mRNA expression values for perforin, granzyme B, TNF-β and FasL in CD8+HLA-DR+T cells in the untreated SAA group were 0.66±0.25, 0.56±0.26, 0.61±0.16, 0.77±0.24, respectively, which were significantly higher than those in the control group (0.53±0.14, 0.40±0.13, 0.46±0.15, 0.58±0.16). (P < 0.05). The apoptosis values in SAA group 1 (CD8+HLA-DR+ T cells from untreated SAA patients and CD3- bone marrow mononuclear cells from remission patients), SAA group 2 (CD8+HLA-DR+ T cells from untreated SAA patients and CD3- bone marrow mononuclear cells from normal controls), the remission group (CD8+HLA-DR+ T cells and CD3- bone marrow mononuclear cells from remission patients) and the normal control (CD8+HLA-DR+ T cells and CD3- bone marrow mononuclear cells from normal controls) were 41.12 ± 24.84%, 45.81 ± 20.47%, 35.03 ± 22.09%, 20.95 ± 13.82%. There were no significant differences between SAA group 1, SAA group 2, and the remission group (P > 0.05). However, the apoptosis in each of these groups was higher than in the normal control (P < 0.05). The LDH levels in SAA group 1, SAA group 2, the remission group and normal control were 74.56 ± 49.13 U/L, 62.61 ± 31.76 U/L, 61.06 ± 28.41 U/L, and 28.60 ± 8.91 U/L. There were no significant differences between SAA group 1, SAA group 2, and the remission group (P > 0.05). However, the level of LDH in these groups was significantly higher than in the normal control (P < 0.05).

CD8+HLA-DR+T cells might contribute to bone marrow failure in SAA. Immunosuppressive therapy dramatically reduced the quantity and function of CD8+HLA-DR+T cells, and inhibitors of CD8+HLA-DR+T cells or other factors involved in this pathway will be attractive therapeutic targets in SAA.

No relevant conflicts of interest to declare.