The composite interleukin-1 genotype in South Africa

The objective of this study was to evaluate the association between the interleukin-1 composite gene polymorphism and the severity of periodontal disease in the Xhosa population of South Africa.

Periodontitis is a bacterially-induced chronic inflammatory disease that destroys the tooth supporting tissues. A specific pattern of interleukin-1 polymorphisms (known as the composite IL-1 genotype) has been found to influence the severity of chronic periodontitis in some ethnic groups.

Ninety-nine subjects, 35-60 years of age, of Xhosa descent, who were non-smokers and free of systemic disease, were enrolled in a case-control study depending on their periodontal status (healthy to mild vs. moderate to severe disease). A buccal smear was obtained from each subject; the DNA was isolated then amplified using the polymerase chain reaction (PCR). Allele identification was either by real-time PCR or by size fractionation following restriction digestion and separation on a polyacrylamide gel.

The prevalence of the composite genotype was only 6% in the 99 subjects of the study population, which occurred more frequently in "cases" (8.2%) than in "controls" (4%). The frequency of IL-1A +4845 allele 2 genotype was 47% in cases and 22% in controls (p = 0.009), and that for IL-1B +3954 was 14.3% in cases and 20% in controls (p = 0.595).

This study demonstrated that the IL-1 composite polymorphism occurred among only few subjects in the Xhosa population of South Africa, and so was not significantly associated with the severity of chronic periodontitis in this population.