OBJECTIVETo explore the apoptosis and its mechanisms of spleen CD4⁺ CD25⁺ regulatory T (Treg) cells in severe aplastic anemia (SAA) mouse model induced by interferon (IFN-γ) in combination with busulphan (BU).

METHODSThe BALB/c female mice SAA model was induced by intraperitoneal injection with IFN-γ and intragastric administration with BU (combined group, n=16), with BU group (n=16), IFN-γ group (n=16) and normal group (n=16) as controls. Spleen Treg cells were purified by using of immunomagnetic beads. Apoptosis was detected by flow cytometry. AKt and TGF-β expression was measured by Western blot.

RESULTSApoptosis of spleen Treg cells in combined group [(33.21±0.65)%] was significantly higher than that in BU group [(21.58±0.64)%], IFN-γ group [(17.62±1.05)%], and control[(27.38±1.89)%] (P<0.05). A significantly lower expression of AKt and TGF-β protein was also seen in combined group (0.30±0.05 and 0.17±0.05), as compared to the other three groups (P<0.05).

CONCLUSIONExcessive apoptosis of Treg cells was found in SAA mouse model, which may be a cause of Treg cells decrease in patients with AA. The down-regulated expression of AKt and TGF-β could play a role in increased apoptosis of Treg cells. Our data may provide a new treatment strategy in AA.