Objective To sudy the changes in mTOR signaling pathway in childhood aplastic anemia(AA) by detecting the expression levels of the molecules of mTOR signaling pathway in T cells,and to explore immunologoical pathogenesis of AA in children from T cell intracellular signal transduction pathway.Methods Peripheral blood samples were collected from 16 newly diagnosed severe AA(SAA) patients and 8 patiens treated with effective immunosuppressive therapy,and the findings were compared with those of 17 healthy children (normal controls) and CEM cells (positive controls).The expressions of p-Akt,p-TSC2,p-mTORC1,p-4EBP1,p-p70S6K in CD3 + T cells in peripheral blood were detected by flow cytometry(FCM).Results 1.The expressions of p-Akt,p-TSC2,p-mTORC1,p-4EBP1,pp70S6K of the newly diagnosed SAA group were higher than those of the normal control group (P ＜ 0.05),but were lower than the postive control group (CEM group) (P ＜ 0.05).The mean fluorescence intensity (MFI) of p-Akt of three groups was 8.04 ± 3.78,2.59 ± 1.01 and 20.23 ± 8.98 respectively ;p-TSC2 was 49.73 ± 19.49,16.10 ± 8.04 and 101.05 ± 29.78 respectively ; p-mTOR was 13.90 ± 9.32,2.92 ± 1.09 and 34.3 ± 19.03 ;p-4EBP1 was 142.69 ± 53.36,26.91 ± 13.70,256.01 ± 53.79 ; p-p70S6 K were 17.67 ± 10.48,3.69 ± 2.22,31.73 ± 12.85 respectively.2.The expressions of p-Akt,p-TSC2,p-mTORC1,p-4EBP1,p-p70S6K of the effective treatment groups were lower than those of the newly diagnosed SAA group (P ＜ 0.05) ; the expressions of p-Akt,p-TSC2,p-mTORC1,p-p70S6K were similar to those of the normal control group(P ＞ 0.05),but the expressions of p-4EBP1 were higher(P ＜ 0.05).The MFI was followed by 3.28 ± 1.27,16.50 ± 10.91,3.54 ± 1.66,74.89 ± 49.69 and 4.21 ± 1.69.Conclusions 1.The expressions of p-Akt,p-TSC2,p-mTORC1,p-4EBP1,p-p70S6K were increased in the newly diagnosed SAA patients,the mTOR signaling pathway was activated in SAA patients.2.The expressions of p-Akt,p-TSC2,p-mTORC1,p4EBP1,p-p70S6K were lower than those of the newly diagnosed SAA patients.The degree of activation of mTOR signaling pathway was associated with disease status.The signaling pathways may be involved in the T cells of AA of the immune abnormalities.