IMMUNOBIOLOGY Functional characterization of CD4 T cells in aplastic anemia

The role of CD4 T cells in the pathogene-sis of aplastic anemia (AA) is not well characterized. We investigate CD4 T-cell subsets in AA. Sixty-three patients with acquired AA were studied. Th1 and Th2 cells were significantly higher in AA pa-tients than in healthy donors (HDs; P .03 and P .006). Tregs were significantly lower in patients with severe AA than in HDs (P <.001) and patients with non-severe AA (P .01). Th17 cells were in-creased in severe AA (P .02) but normal in non-severe AA. Activated and resting Tregs were reduced in AA (P .004; P .01), whereas cytokine-secreting non-Tregs were increased (P .003). Tregs from AA patients were unable to sup-press normal effector T cells. In contrast, AA effector T cells were suppressible by Tregs from HDs. Th1 clonality in AA, investigated by high-throughput sequenc-ing, was greater than in HDs (P .03). Our results confirm that Th1 and Th2 cells are expanded and Tregs are function-ally abnormal in AA. The clonally re-stricted expansion of Th1 cells is most likely to be antigen-driven, and induces an inflammatory environment, that exac-erbate the functional impairment of Tregs, which are reduced in number. (Blood. 2012;119(9):2033-2043