Human CD90 identifies Th17/Tc17 T cell subsets that are depleted in HIV-infected patients

By revisiting CD90, a GPI-anchored glycoprotein, we show that CD90 is expressed by a subset of CD4 ⁺ and CD8 ⁺ human T cells. CD4 ⁺CD90 ⁺ cells share similarities with Th17 cells because they express the Th17-specific transcription factor RORC2 and produce IL-17A. CD4 ⁺CD90 ⁺ cells are activated memory T cells that express the gut mucosal markers CCR6, CD161, and the α ₄ and β ₇ integrins. Compared with CD90-depleted CCR6 ⁺ memory Th17 cells, CD4 ⁺CD90 ⁺ cells express higher levels of IL-22 and proinflammatory cytokines (IL-6, TNF-α and GM-CSF), but they produce lower levels of IL-21 and no IL-9. Analyses of CD8 ⁺CD90 ⁺ cells reveal that they express RORC2 and are able to produce higher levels of IL-17A, IL-22, and CCL20 compared with CD90-depleted CD8 ⁺ cells. These data show that CD90 identifies Th17 and Tc17 cells with a peculiar cytokine profile. Studies of circulating CD90 ⁺ cells in HIV patients show that CD90 ⁺ cells are decreased with an imbalance of the CD4 ⁺CD90 ⁺/regulatory T cell ratio in nontreated patients compared with treated patients and healthy donors. Overall, human CD90 identifies a subset of Th17 and Tc17 cells within CD4 ⁺ and CD8 ⁺ T cells, respectively, which are depleted during HIV infection.