Objective To explore the possible role of proline-rich tyrosine kinase (Pyk2) in the pathogenesis of systemic lupus erythematosus (SLE).Methods The expression of Pyk2 in the peripheral blood mononuclear cells (PBMCs) of 50 patients with SLE and 36 healthy controls were tested with RT-PCR assay.The activation of Pyk2 was inhibited using specific inhibitor Pyk2 (TyrA9).Semi-quantitative PCR methodwas used to detect the Blys expression of PBMCs.One-way ANOVA and Pearson's correlation analysis were used for statistical analysis.Results The Pyk2 expression level (28.31 ±0.91) of SLE patients was significantly higher than that in healthy controls (33.69±0.04),the difference was statistically significant (P＜0.05).The activation of Pyk2 was stimulated and the expression levels of Blys in the PBMCs of patients with SLE was elevated.By inhibiting the activation of Pyk2,the BLyS expression levels decreased significantly.Conclusion Pyk2 may be involved in the abnormal activation of lymphocytes which lead to the pathogenesis of SLE.Pyk2 expression is associated with SLE disease activity,disease aggravation,and the Pyk2 expression levels is also increased significantly.In addition,the expression level of Pyk2 is higher in patients with renal involvement than those patients with other organ involvement.