Polymorphism in the T-cell regulatory gene CTLA4 and aggressive periodontitis

Objectives: CTLA4 is a negative regulator of immune responses mediated by T-cells and is encoded by a gene with common allelic forms which influence gene expression characteristics. T-cells play a central role in the initiation and progression of human periodontal disease, therefore we aimed to investigate the possible association of CTLA4 genotype with aggressive periodontitis. We chose to analyse the CT60 single nucleotide polymorphism (SNP) in the CTLA4 locus. Carriage of the G allele at this SNP has previously been associated with susceptibility to various autoimmune diseases and represents a candidate marker for cross-susceptibility to immune-mediated human disease.

Methods: A novel RFLP-PCR method was developed to identify alleles of the CT60 in DNA samples from healthy volunteers and a panel of DNA samples from patients with aggressive periodontitis. Differences in the distribution of genotypes and alleles between control and disease groups were analysed by Chi-square analysis. The SNP analysis was validated in 2 independent panels of control DNA samples; the distribution of CT60 genotypes in these samples was in Hardy Weinberg equilibrium and frequencies consistent with previously published data.

Results: In the pooled control sample (n=132) the A/A, A/G and G/G CT60 genotypes had frequencies of 18.9%, 52.3% and 28.8% respectively and in the aggressive periodontitis patients (n=79) the frequencies were 20.2%, 53.2% and 26.6% respectively. The differences between the genotype distributions were not significantly different (P>0.5) and there were no significant differences in the carriage of the G allele (OR=1.09; P>0.5).

Conclusion: The results of this study suggest that the CT60 SNP does not have a major influence on susceptibility to aggressive periodontitis.