Objective To investigate the clinical significance of abnormally expressed PD-1 on CD 4+CD 2 8+/-T cells in peripheral blood of patients with systemic lupus erythematosus ( SLE ) . Methods Peripheral blood samples were collected form 50 patients with primary SLE and 40 healthy subjects and used to isolated mononuclear cells. Expression of CD4+CD28-, CD4+CD28+, CD4+CD28+PD-1+and CD4+CD28-PD-1+T cells in peripheral blood samples of the two groups were detected by flow cytometry. Clinical data of SLE patients were collected. Based on SLE disease activity index (SLEDAI), SLE patients were classified into two groups: stable group (SLEDAI<10) and active group (SLEDAI≥10). Based on the condition of renal damage, they were also divided into two groups: lupus nephritis group and non-lupus ne-phritis group. Differences in T cell expression were compared among these groups. Statistical analysis was performed to analyze the relationships of different T cell subsets with laboratory and clinical parameters rela-ting to SLE and SLEDAI. Results The percentages of peripheral CD4+CD28-, CD4+CD28+PD-1+and CD4+CD28-PD-1+T cells of active group were higher than those of stable and healthy control groups ( P<0. 05). Moreover, patients with lupus nephritis had higher percentages of these T cell subsets than those without (P<0. 01). SLE patients who were positive for anti-dsDNA or anti-SmRNP antibody, or had de-creased complement C3, thrombocytopenia or decreased lymphocytes had higher percentages peripheral CD4+CD28-T cells than those in the corresponding negative group. SLE patients who were positive for anti-dsDNA or anti-SmRNP antibody, or had decreased complement C3, complement C4 or lymphocytes showed en-hanced expression of peripheral CD4+CD28+PD-1+T cells as compared with those in the corresponding nega-tive group. SLE patients positive for anti-dsDNA antibody, or with decreased complement C3 or lymphocytes or suffering from alopecia had higher percentages of peripheral CD4+CD28-PD-1+T cell than those in the cor-responding negative group. Differences between different groups were statistically significant (P<0. 05). Conclusion Abnormal expression of CD4+CD28-T cells and PD-1 on CD4+CD28-and CD4+CD28+T cells in peripheral blood of patients with SLE has certain correlation with laboratory parameters and clinical indicators.