The association of CD40 polymorphism (rs1883832C/T) and soluble CD40 with the risk of systemic lupus erythematosus among Egyptian patients.

BACKGROUND: Systemic lupus erythematosus (SLE) is a complex autoimmune disorder of unknown etiology. Considerable evidence supports a genetic basis for susceptibility to SLE. Genetic and functional data suggested the CD40 receptor (CD40) and CD40 ligand (CD40L) as strong candidate genes for SLE.

AIM: To investigate whether CD40 gene rs1883832 C/T single-nucleotide polymorphism (SNP) and/or soluble CD40 (sCD40) are associated with SLE in the Egyptian population.

SUBJECTS AND METHODS: The study included a hundred SLE patients, and a fifty age- and gender-matched healthy control subjects. CD40 gene rs1883832 C/T genotyping was carried out using restriction fragment length polymorphism (RFLP), while sCD40 levels were measured by ELISA.

RESULTS: CD40 rs1883832C/T genotypes (CC, TT, and CT) as well as CD40 alleles (C and T) did not differ between SLE patients and normal control (p = 0.63, 0.37, and 0.31 respectively). Though did not reach statistical significance, carriers of genotype CT had 1.5 times more chance to develop SLE compared to wild homozygous CC genotype carriers (OR 1.44), while carriers of genotype TT had ~ 2 times more chance to have SLE than CC carries (OR 1.96). Accordingly, the carriers of the T allele had ¬ 1.5 times more chance to get SLE compared to the carriers of the C allele (OR 1.4). The serum sCD40 level was significantly higher in SLE patients compared to healthy control (3.4 vs. 0.8 ng/mL, p < 0.001). In SLE patients, using CC as the reference genotype, serum sCD40 level was significantly higher in the carriers of the homozygous genotype TT (3.8 ± 1.3 vs. 2.9 ± 1.9, p = 0.0001), and T allele (3.6 ± 1.4 vs. 3.0 ± 1.5, p = 0.003). Moreover, sCD40 could discriminate SLE patients from normal subjects at a cutoff value of 0.885 ng/mL with 98% sensitivity and 96% specificity (AUC = 0.999, p < 0.001).

CONCLUSIONS: The study did not prove CD40 gene (rs1883832 C/T) polymorphism as a clear risk factor of SLE in this cohort of Egyptian patients, though it was highly likely associated with the carriers of T allele. In the same context, significant high sCD40 levels were observed in the T allele carriers.