Background Inhibition of the key costimulatory signals results in T cell anergy,indicating the alloantigen-specificimmunologic unresponsiveness.In this study,the effect of blockage of costimulatory signal CD_(86)on murineabortion-prone model was studied.Methods Thirty CBA/J female mice cohabitated with DBA/2 male or BALB/c male mice were investigated.CBA/JxDBA/2 matings were used as the abortion-prone model,and CBA/J x BALB/c matings were used as the normalpregnant model.The abortion-prone models were divided into experimental and control groups,and the normal pregnantmodels were set as a normal group(10 mice in each group).The mice in the experimental group were treated withanti-mouse CDas monoclonal antibody(mAb)(100 μg)on day 4.5 of gestation,while the controls receivedirrelevant-isotype matched rat IgG2b.AS for the normal group,nothing was given to the mice.The mice were killed on day13.5 of gestation,embryo resorption rate and the expression of transforming growth factor β_1(TGF-β_1),plasminogenactivator inhibitor 1(PAl-1),and matrix metalloproteinase 9(MMP-9)were detected.Then the data were analyzed byChi-square test and Fisher’s exact test.Results The embryo resorption rate in the experimental(8.2%)and normal groups(7.7%)was significantly lower thanthat of the control(23.5%,P<0.05).No significant difference was detected between the experimental and normal groups(P>0.05).The positive expression rates of TGF-β_1 and PAl-1 proteins in the experimental and normal groups weresignificantly higher than those in the control group(P<0.05).The positive expression rate of MMP-9 protein in theexperimental and normal groups was significantly lower than that in the control group(P<0.05).No significant differencein the positive expression rates of the three proteins was detected between the experimental and normal groups(P>0.05).Conclusions Blockage of costimulatory signal CD_(86)at early pregnancy can treat uncertain recurrent spontaneousabortion by stimulating the expression of TGF-β_1,MMP-9 and PAl-1 and reducing the embryo resorption rate. Background Inhibition of the key costimulatory signals results in T cell anergy, indicating the alloantigen-specific immunologic unresponsiveness. In this study, the effect of blockage of costimulatory signal CD_ (86) on murine abortion-prone model was studied. Methods Thirty CBA / J female mice cohabitated with DBA / 2 male or BALB / c male mice were investigated. CBA / JxDBA/2 matings were used as the abortion-prone model, and CBA / J x BALB / c matings were used as the normal pregn model. The abortion-prone The models were divided into experimental and control groups, and the normal pregnantmodels were set as a normal group (10 mice in each group). The mice in the experimental group were treated withanti-mouse CDas monoclonal antibody (mAb) (100 μg) on ​​day 4.5 of gestation, while the controls receivedirrelevant-isotype matched rat IgG2b.AS for the normal group, nothing was given to the mice. The mice were killed on day 13.5 of gestation, embryo resorption rate and the expression of transforming growth factor β_1 ( TGF Plasminogenactivator inhibitor 1 (PAl-1), and matrix metalloproteinase 9 (MMP-9) were detected. The data were analyzed by Chi-square test and Fisher’s exact test. Results The embryo resorption rate in the experimental (8.2% ) and normal groups (7.7%) were significantly lower thanthat of the control (23.5%, P <0.05) .No significant difference was detected between the experimental and normal groups (P> 0.05). The positive expression rates of TGF- PAl-1 proteins in the experimental and normal groups weresignificantly higher than those in the control group (P <0.05). The positive expression rate of MMP-9 protein in the experimental and normal groups was significantly lower than that in the control group (P < 0.05) .No significant difference in the positive expression rates of the three proteins was detected between the experimental and normal groups (P> 0.05) .Conclusions Blockage of costimulatory signal CD_ (86) at early pregnancy can treat uncertain recurrent spontaneous abortion by stimulating the exp ression of TGF-β_1, MMP-9 and PAl-1 and reducing the embryo resorption rate.