Objective:To investigate changes of T lymphocyte subsets and T lymphocytes apoptosis in sepsis and to discuss its role in immunosuppression and prognosis. Methods:Totally 55 sepsis patients from Intensive Care Unit of The First Affiliated Hospital of Chongqing Medical University from October 1

2014 to December 31

2015

were enrolled. Sepsis patients were divided into survival group and death group according to their prognosis. The APACHEⅡ score was calculated and the risk of death(R)was predicated according to APACHE Ⅱ score

and the survival rate of 28 days were followed up. The absolute counts of peripheral blood T-lymphocyte subsets were measured by flow cytometry;T-lymphocyte apoptosis were detected by flow cytometry and TUNELassay. Immortalized line of human T lymphocyte cells(Jurkat)was cultured and cells were treated with serum from sepsis patients or healthy control subjects

then apoptosis was measured by flow cytometry and TUNEL assay. Cleaved-caspase 3

B-cell lymphoma-2(Bcl-2)and myeloid cell leukemia 1(Mcl-1)expressions were detected by Western blot analysis. Results:Absolute counts of peripheral blood T lymphocyte subsets in survival group and death group were decreased as compared with those in control group:CD3+cell counts were respectively 374.0(274.5-514.0)

154.0(87.5-256.2)

1534.5(1255.0-1756.7);CD3+CD4+ cell counts were respectively 198.0(148.5-299.0)

68.0(37.7-108.5)

766.5(629.3-923.5);CD3+CD8+ cell counts were respectively 142.0(89.0-184.0)

76.0(48.7-134.5)

600.5(400.2-717.0)(P<0.05). Compared with those in survival group

CD3+ and CD3+CD4+ cell counts decreased more obviously in death group(P=0.011

P=0.005). CD3+CD4+ proportion was lower in death group(42.40±5.71)% than in control group(53.46±9.28)%;CD3+CD8+ proportion was obviously higher in death group(54.40±4.76)% than in control group(39.33±7.26)%;CD4+/CD8+ratio was significantly lower in death group(0.79±0.17)than in control group(1.44±0.51)(P=0.003

P=0.003

P=0.023).CD3+

CD3+CD4+

CD3+CD8+ and CD4+/CD8+ ratio exhibited a negative relationship with APACHEⅡscore and predicted risk of death score(R)(P<0.05). CD3+ T-lymphocyte apoptosis ratio in survival group(15.59 ±0.54)% and death group(39.57 ±4.49)%both increased as compared with that in control group(9.53 ±1.91)%(P=0.040

P=0.000). Apoptosis ratio of CD3+ T-lymphocyte in death group increased more obviously than that in survival group(P=0.000). Apoptosis ratio of Jurkat cell induced by serum from survival group(16.60±3.55)% and death group(32.93 ±5.89)% both increased obviously as compared with that in control group(8.56±0.89)%(P=0.049

P=0.000). Protein expressions of Cleaved-caspase 3 in survival group(2.01±0.21)and death group(2.68±0.28)were obviously higher than those in control group(P=0.001

P=0.000). Mcl-1 expressions in survival group(0.77±0.03)and death group(0.61±0.01)were lower than those in control group(P=0.000

P=0.000). Bcl-2 expressions in survival group(0.68±0.07) and death group(0.48 ±0.03) were lower than those in control group(P =0.000

P =0.000). Compared with those in survival group

the changes of apoptosis rate

Cleaved-caspase3

Mcl-1 and Bcl-2 in Jurkat cell were more obvious in death group(P=0.002

P=0.007

P=0.000

P=0.001). Conclusion:Declined T-lymphocyte cell counts and increased T lymphocyte apoptosis induce immunosuppression in sepsis

which are related to the severity of illness and prognosis.