Objective:To explore the clinical application effect of belimumab in the treatment of systemic lupus erythematosus(SLE)and its influence on cluster of differentiation(CD40)and cluster of differentiation 40 ligands(CD40L)expression in the peripheral blood,and to provide a theoretical basis for the effective treatment of SLE.Methods:A retrospective analysis was conducted on the clinical data of 150 patients with SLE admitted to our hospital,and they were divided into conventional treatment group(n=78,standard treatment plan)and belimumab group(n=72,standard treatment plan+belimumab)according to the treatment methods.The therapeutic effects and adverse reactions were compared.The clinical symptoms,organ involvement,disease activities,prednisone doses,the expression levels of CD40 and CD40L mRNA in peripheral blood mononuclear cells,and the levels of immunology-related indicators before and after treatment were analyzed.Results:Compared with conventional treatment group,the total effective rate,complement C3 and complement C4 levels in the belimumab group were significantly increased after treatment(P<0.01 or P<0.001),while the proportion of renal involvement,the SLE disease activity index-2K(SLEDAI-2K)score,the dosage of prednisone,immunoglobulin G(IgG)level and the expression levels of CD40 and CD40L mRNA in peripheral blood mononuclear cells were decreased(P<0.01 or P<0.001).There was no statistically significant difference in the total incidence of adverse reactions between two groups during treatment period(P>0.05).Conclusion:Belimumab can increase the effective rate of SLE treatment,reduce disease activity,decrease the involvement of the kidneys and the dose of hormones,and has good safety;its mechanism of action may be related to down-regulating the expression of CD40 and CD40L in peripheral blood and improving the immune function.