Objectives To observe the apoptosis and apoptosis related Fas/bcl 2 expression in the peripheral blood lymphocytes from patients with lupus systemic erythematosus (SLE), and to evaluate its clinical significance Methods Twenty nine patients with SLE,11 patients with rheumatoid arthritis (RA), and 11 sex and age matched healthy individuals were included in this investigation Peripheral blood mononuclear cells were isolated by Ficoll Hypaque sedimentation and monocytes were removed by plastic adherence Lymphocytes were incubated in vitro in RPMI 1640 with 10% FSC for 48 hours Before and after culture, terminal deoxynucleotidyl transferase mediated nick end labelling (TUNEL) technique combined with flow cytometry (FCM) was used to detect the apoptotic cells Immunohistochemistry ABC was used to detect the expression of bcl 2 and Fas antigen Apoptosis rate was estimated by calculating the percentage of apoptotic cells in total cells The disease severity was assessed by analysing the scores accodring to SLEDAI Results Apoptosis rates detected by TUNEL and FCM were well consistent Before culture the PBL apoptosis rate in SLE group was 1 58%±0 89%, which was significantly higher than that in normal controls (0 8%±0 39%, P <0 001) and in RA group (0 82%±0 52%, P <0 001) After 48 hour culture in vitro, the apoptosis rate was further increased in SLE patients (28 17%±9 95%), which was much higher than that in normal controls and RA group (11%±1 53%, 10 35%±1 24%, P <0 001, respectively) There was no significant difference of apoptosis rates in normal control and RA group Among SLE patients the rate of active was higher than that of inactive There was a significant correlation between SLE severity and apoptosis rate in vitro (r=0 866, P <0 001) Both the expressions of bcl 2 and Fas in PBL of patients with SLE were more significant than those in normal controls (bcl 2, 31 48%±15 04% vs 18 36%±3 44%; Fas, 35 03%±14 58% vs 18 18%±3 09%, P <0 01, P <0 001, respectively), menwhile these expressions in active SLE were higher than those in inactive SLE (bcl 2,37 44%±5 57% vs 24 15%±5 57%, P <0 05; Fas, 41 69%±14 65% vs 26 84%±9 78%, P <0 001) Conclusions SLE is an autoimmune disease characterized by over synthesis of antibodies along with decreased lymphocyte proliferation and reduced cytokine production It is suggested that lymphocyte apoptosis may play an important role in the disturbance of lymphocyte function Our results provided further evidence for the assumption that lymphocyte apoptosis takes part in the pathogenesis of SLE Furthermore, we found that increased rate of apoptosis could be used as a clinic index for evaluating and monitoring the severity of SLE Objectives To observe the apoptosis and apoptosis related Fas / bcl 2 expression in the peripheral blood lymphocytes from patients with lupus systemic erythematosus (SLE), and to evaluate its clinical significance Methods Twenty nine patients with SLE, 11 patients with rheumatoid arthritis (RA), and 11 sex and age matched healthy individuals were included in this investigation Peripheral blood mononuclear cells were isolated by Ficoll Hypaque sedimentation and monocytes were removed by plastic adherence Lymphocytes were incubated in vitro in RPMI 1640 with 10% FSC for 48 hours Before and after culture, terminal deoxynucleotidyl transferase mediated nick end labeling (TUNEL) technique combined with flow cytometry (FCM) was used to detect the apoptotic cells Immunohistochemistry ABC was used to detect the expression of bcl 2 and Fas antigen Apoptosis rate was estimated by calculating the percentage of apoptotic cells in total cells The disease severity was assessed by analysing the scores accodring to SLEDAI Results Apoptosis rates detected by TUNEL and FCM were well consistent before culture the PBL apoptosis rate in SLE group was 1 58% ± 0 89%, which was significantly higher than that in normal controls (0 8% ± After 48 hour culture in vitro, the apoptosis rate was further increased in SLE patients (28 17% ± 9 95%, P 0 001) and in RA group (0 82% ± 0 52%, P 0 001) %), which was much higher than that in normal controls and RA group (11% ± 1 53%, 10 35% ± 1 24%, P <001 1 respectively) There was no significant difference of apoptosis rates in normal control and RA group Among SLE patients the rate of active was higher than that of inactive There was a significant correlation between SLE severity and apoptosis rate in vitro (r = 0 866, P <001 1) Both the expressions of bcl 2 and Fas in PBL of patients with SLE were more significant than those in normal controls (bcl 2, 31 48% ± 15 04% vs 18 36% ± 3 44%; Fas, 35 03% ± 14 58% vs 18 18% ± 3 09%, P <0 01, P <0 001, respectively), while these expressions in active SLE were higher than those in inactive SLE (bcl 2, 447% P <0.05; Fas, 41 69% ± 14 65% vs 26 84% ± 9 78%, P <0.001) Conclusions SLE is an autoimmune disease characterized by over synthesis of antibodies along with decreased lymphocyte apoptosis and play an important role in the disturbance of lymphocyte function Our results provided further evidence for the assumption that lymphocyte apoptosis takes part in the pathogenesis of SLE Furthermore, we found that increased rate of apoptosis could be used as a clinic index for evaluating and monitoring the severity of SLE