Analysis of peripheral blood lymphocyte subsets and its correlation with the rapid plasma reagin titers in serofast syphilis patients

Abstract

Objective To investigate the reason of persisting positive rapid plasma reagin (RPR) in serofast syphilis patients, and to provide reference for clinical treatment and prognosis. Methods A total of 33 serofast patients and 23 healthy controls were enrolled in this study. The percentages and absolute counts of CD3+ , CD4+ , CD8+ T lymphocytes and natural killer (NK) cells were detected by flow cytometry. The comparison of two groups was analyzed by independent sample t test, and the correlation between change of lymphocyte subgroups and RPR titer in serofast syphilis patients was analyzed by bivariate linear correlation method. Results Compared with healthy controls, the percentages of CD3+ , CD8+ T lymphocytes in serofast syphilis group were both increased significantly (75.75±5.76)% vs (68.37±5.80)%, (t=4.69, P<0.01); (27.34±7.02)% vs (24.33±1.95)%, (t=2.34, P=0.025), while both the percentage and absolute count of NK cells were significantly decreased (7.32±4.48)% vs (14.87±6.26)%, (t=5.269, P<0.01); (136.2±83.4)/μL vs (298.8±166.9)/μL, (t=4.311, P<0.01). RPR titer of the patients was negatively correlated with both percentage and absolute count of CD4+ T lymphocytes (r=-0.476 and -0.515, respectively, both P<0.01), and it was positively correlated of CD8+ lymphocytes (r=0.588 and 0.305, P<0.01 and P=0.804). Conclusion The imbalance of immune response of lymphocyte subsets observed in serofast syphilis may explain the RPR titers change. Key words: Syphilis; Serofast; Rapid plasma reagin; Lymphocyte subsets; Flow cytometry instrument