Azacitidine differentially affects CD4(pos) T-cell polarization in vitro and in vivo in high risk myelodysplastic syndromes.

CD4(pos) T-cell subsets play a role in myelodysplastic syndromes (MDS) pathogenesis and may be affected upon 5-azacitidine (Aza) treatment. Aza enhanced human T(H)1 frequencies in vitro but not in vivo. The proportion of functional FoxP3(pos) regulatory T cells (Treg) was enhanced by Aza in vitro (p < 0.0002), and a modest, temporary increase was observed in vivo (p = 0.08). The overall number of T(H)17 was reduced both in vitro (p < 0.03) and in vivo (p < 0.006), indicating that Aza directly affects CD4(pos) polarization during activation in vitro. Upon in vivo treatment in high risk MDS patients, particularly the T(H)17-Treg axis is affected.