AimCurrent evidence suggests the cluster of differentiation 40 and ligand (CD40/CD40L) pathway as a key process in the development, progression, and outcome of acute coronary syndrome (ACS).The aim was to investigate the prognostic importance of soluble CD40L (sCD40L) levels, single nucleotide polymorphisms (SNP) in the CD40LG gene, and the relation between sCD40L and SNPs in patients with ACS.MethodsSamples were obtained on admission from 482 patients with ACS in Beijing Anzhen hospital.Results(1)In total, 6.8% (n=33) of the patients had undetectable (<95 ng/L) sCD40L.The average level of sCD40L in 449 patients was 296±25 ng/L, the average level of sCD40L in male (309 ng/L) were higer than that in female (195 ng/L), sCD40L levels were associated with the severity of ACS （p<0.001）.(2)The distribution of cCD40L were different among SNP polymorphism of CD40LG, patients with GG genotype showed the highest level of sCD40L （p<0.001）.(3)After adjustment of age, sex, and related risk factors, polymorphism of CD40LG was related significantly with the severity of ACS, ratio odds were 1.00, 1.32, 3.41 (p≤0.001) respectively.ConclusionWe identified a SNP in the CD40LG gene as a novel regulator of sCD40L plasma concentrations and a predictor of the severity of ACS.