〔Abstract〕 Objective To investigate the expression of programmed death 1(PD1) on CXCR5-CD4+T cells from the patients with systemic lupus erythematosus(SLE) and to analyze the clinical relevance to disease severity. Methods The expression of PD1 on CXCR5-CD4+T cells was examined from 47 SLE patients and 35 healthy controls(HC) by the technique of flow cytometry. The expression of PD1 including percentage of PD1+CXCR5-CD4+T cells and mean fluorescence intensity(MFI) on CXCR5-CD4+T cells was compared between SLE patients and HC. And its correlation with clinical indicators, laboratory inspection and the percentage of plasmablasts was analyzed. Moreover, the predictive value of the expression of PD1 on CXCR5-CD4+T cell was explored. Results (1) The percentage of PD1+CXCR5-CD4+T cells from SLE patients significantly elevated compared with HC(P=0.008 3,U=540.5), and the MFI of PD1 on CXCR5-CD4+T cells from SLE patients significantly elevated compared with HC(P<0.000 1,U=187.0).(2) The percentage of PD1+CXCR5-CD4+T cells was associated with C3(r s =-0.335 2,P=0.022 8), anti-SSA(P=0.016 6,t=2.5), anti-histone(P=0.030 3,t=2.3), treatment(P=0.020 2,t=3.4), plasmablasts(r s =0.387 1,P=0.0072) in SLE patients. The MFI of PD1 on CXCR5-CD4+T cells was associated with SLEDAI(r s =0.403 1,P=0.005 0), ESR(r s =0.356 1,P=0.017 7), CRP(r s =0.337 4,P=0.028 9), RBC(r s =-0.297 0,P=0.042 6), HGB(r s =-0.302 9,P=0.038 5), HCT(r s =-0.381 6,P=0.008 1), L(r s =-0.393 7,P=0.006 2), L%(r s =-0.391 2,P=0.006 5), N%(r s =0.315 0,P=0.031 1), NLR(r s =0.373 0,P=0.009 8), LMR(r s =-0.431 5,P=0.002 5), dNLR(r s =0.315 0,P=0.031 1), anti-Ro52(P=0.029 5,t=63.5), treatment(P=0.035 5, W=21), plasmablasts(r s =0.315 8,P=0.030 6).(3) Logistic regression analysis showed that the MFI of PD1 on CXCR5-CD4+T cells was a risk factor for SLE.(4) ROC analysis showed the AUC of the MFI of PD1 on CXCR5-CD4+T cells was 0.886. A further established model based on combination of the MFI of PD1 on CXCR5-CD4+T cells and HGB showed predictive value in distinguishing SLE from HC with AUC of 0.979. And predictive value was positively associated with SLEDAI(r s =0.313 6,P=0.030 3). Conclusion Increased percentage of PD1+CXCR5-CD4+T cells and increased MFI of PD1 on CXCR5-CD4+T cells in SLE are associated with disease severity and activity, and a model based on combination of the MFI of PD1 on CXCR5-CD4+T cells and HGB shows prominent value for predicting SLE.