The genetic impact of the Q551R interleukin-4 receptor alpha polymorphism for aggressive or chronic periodontitis and the occurrence of periodontopathic bacteria.

OBJECTIVE: The Q551R polymorphism of the gene encoded for the α chain of the interleukin-4 receptor (IL-4RA) could influence both IL-4 and IL-13 signalling. Since both cytokines could be important in the pathogenesis of periodontitis the aim of this study was to evaluate putative associations of the Q551R polymorphism to generalized aggressive or chronic periodontitis and five periodontopathogens.

DESIGN: 154 patients with severe generalized periodontitis (chronic: n=68, mean age=48.7 ± 9.4 years; aggressive: n=86, mean age=40.4 ± 9.8 years) and controls without periodontitis (n=89, mean age=46.2 ± 10.8 years) were included. The Q551R polymorphism was analysed by PCR-SSP CTS-Kit, Heidelberg, Germany. Subgingival bacteria were determined molecular biologically using micro-Ident test (HainLifescience, Nehren, Germany). Distributions of single alleles and genotypes were calculated by Chi(2)-test with Yates correction or Fisher's exact test. Adjusted odds ratios were generated by logistic regression with respect to established cofactors for periodontitis.

RESULTS: The mutant allele R551 (p(Y)=0.013) and the genotypes QR+RR (p(B)=0.024) occurred more frequently amongst patients with chronic periodontitis vs. controls. Carriers of the Q551R polymorphism had an increased adjusted odds ratio for chronic periodontitis (OR=3.2, 95%CI 1.5-6.5, p=0.002) and severe periodontitis (chronic+aggressive) in general (OR=2.0, 95%CI 1.1-3.6, p=0.003). Moreover, in the total study cohort the Q551R polymorphism was associated with the presence of Tannerella forsythia (90.3% vs. 78.0%, p(Y)=0.01).

CONCLUSIONS: The Q551R IL-4RA polymorphism is a putative risk indicator for severe chronic periodontitis, but was not significant associated to AP.