Interferon-gamma and interleukin-12 gene polymorphisms and their relation to aggressive and chronic periodontitis and key periodontal pathogens.

Background: The gene polymorphisms interferon-gamma (IFN-gamma) 874 T/A and interleukin (IL)-12 1188 A/C have been associated with the altered production of cytokines. Therefore, they might be indicative of the occurrence of chronic periodontitis (CP) or aggressive periodontitis (AgP) and the prevalence of key periodontal pathogens. For this purpose, we analyzed these polymorphisms in subjects with generalized AgP or generalized CP. Moreover, we assessed the relationship between these polymorphisms and five periodontopathic bacteria.

Methods: A total of 124 unrelated German white subjects with periodontitis (AgP=72 and CP=52) and 74 periodontitis-free subjects were studied. Gene polymorphisms were determined by polymerase chain reaction with sequence-specific primers. Subgingival bacteria were molecular biologically analyzed using multiplex polymerase chain reaction and reverse hybridization. The distributions of alleles and genotypes were calculated by the chi(2) test with Yates correction. Risk factor analyses were carried out by logistic regression considering established confounders for periodontitis.

Results: Allele and genotype frequencies of both investigated polymorphisms were not significantly different between subjects with periodontitis and periodontitis-free controls. However, in the total study group, IL-12 AA-positive subjects had a significantly higher bleeding index than individuals who expressed IL-12 CC (68.2% versus 50.0%, P=0.025). Moreover, IFN-gamma AA carriers had a decreased odds ratio (OR) for the individual presence of Aggregatibacter actinomycetemcomitans (previously Actinobacillus actinomycetemcomitans) (OR=0.39, P=0.012) after adjustment for age, gender, smoking, and probing depth. IFN-gamma TA predisposed an individual to infection with Prevotella intermedia (OR=2.15, P=0.019).

Conclusion: Although a relationship between the bleeding index and the presence of bacteria was shown, IFN-gamma and IL-12 polymorphisms are not suitable diagnostic features for AgP and CP.