High-dimensional immune profiling using mass cytometry reveals IL-17A-producing γδ T cells as biomarkers in patients with T-cell-activated idiopathic severe aplastic anemia

Severe aplastic anemia (SAA) is a bone marrow failure syndrome characterized by activated T cells. Features of T-cell activation in the pathophysiology of SAA remain unknown. To understand T cell activation states, we investigated the atlas of peripheral immune cells and the secreted cytokine network with single cell mass cytometry analysis. We found decreased γδ T-cell frequencies in all patients with SAA, together with a significantly increased proportion of interleukin (IL)-17A-producing cell subsets. Cytokine network analysis of immune cells showed significant positive relationship between IL and 17A production from immune cells and disease severity of severe aplastic anemia. On separating SAA into two distinct subgroups based on T-cell activation stage, the proportion of γδ T cells tended to decrease in the T-cell-activated SAA group compared with non-T-cell-activated group. And the proportion of IL-17A-producing γδ T cells (γδT17) within γδ T cells was newly found to be significantly higher in the T-cell-activated SAA group, implying that IL-17A production by γδ T cells was associated with T-cell activation. Overall, our study revealed a role of γδT17 cells in mediating autoreactive T-cell activation in SAA and provided a novel diagnostic indicator for monitoring autoreactive T-cell activation status during the progression of aplastic anemia in the clinic.