Objective       To determine the effect of human augmenter of liver regeneration (hALR) on the proliferation of regulatory T cells and expression levels of the inhibitory cytokines TGF-β1 and IL-10 in ConA-stimulated human peripheral blood mononuclear cells (PBMCs) in order to investigate the underlying immunosuppressive mechanism of hALR.       Methods        PBMCs were isolated from healthy volunteers by gradient centrifugation

and then divided into normal control group

ConA stimulated group and hALR interfering group. Cells in the ConA group and ConA+hALR group were processed by 5 μg/mL ConA and 30 μg/mL hALR

and control group was not treated. After cultured

in vitro

for 60 h

MTS assay [3-(4

5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium

inner salt

]

was used to determine the cellular viability. Flow cytometry (FCM) was used to detect the proportion of CD4

+

CD25

+

FoxP3

+

Treg and the mitotic cycle of Treg. FoxP3 mRNA was detected by real-time fluorescent quantitation PCR

and the levels of TGF-β1 and IL-10 in the supernatant were determined by ELISA.       Results        hALR obviously inhibited the proliferation of ConA-stimulated PBMCs (

P

<

0.01). Compared with the ConA group and control group

hALR significantly increased the proportion of CD4

+

T cells in CD4

+

CD25

+

FoxP3

+

Treg cells (

P

<

0.01) and expression of FoxP3 mRNA . In addition

hALR relieved the G

2

/M cell cycle arrest of Treg induced by ConA

and the levels of TGF-β1 and IL-10 in the supernatant of hALR interfering group

which was significantly higher than ConA group and control (

P

<

0.01).       Conclusion        hALR induces the proliferation and differentiation of Treg

and increases the release of TGF-β1 and IL-10

and thus results in the inhibition of immune response.