Factors which increase the risk of severe adult periodontitis (AP) may also contribute to the success of dental implants. To determine which cytokines may be relevant, levels of interleukin-1alpha (IL-1alpha), interleukin-1beta (IL-1beta), interleukin-1 receptor antagonist (IL-1ra), interleukin-6 (IL-6) and interferon-gamma (IFN-gamma) mRNA were quantitated in gingival tissue from periodontitis patients and healthy controls. Periodontitis significantly increased levels of IL-1alpha, IL-1beta, IL-6 and IFN-gamma mRNA relative to healthy tissues. IL-1 was selected for further study, as it has inflammatory and bone resorbing properties. We examined IL-1A(-889) and IL-1B(+3953) alleles in Caucasian patients with AP and early-onset periodontitis (EOP), patients with dental implants and healthy individuals. The IL-1B(+3953) polymorphism was associated with AP. This was evident from an increased homozygosity for allele 2 in patients with AP and a decreased heterozygosity in advanced AP patients. IL-1A(-889) and a composite genotype [IL-1A(-889)2 plus IL-1B(+3953)2] showed no association with the incidence of periodontitis, disease onset or disease severity. IL-1A(-889), IL-1B(+3953) and the composite genotype also showed no association with failure of dental implants.

A survey of KIR2DL4 polymorphism revealed seven common sequences in the Australian population. The seven sequences encode three different amino acid sequences of the immunoglobulin domains. Two of the sequences encoding different amino acid sequences in the immunoglobulin domains also occur on some chromosomes with a single nucleotide deletion at the end of exon 6, which encodes the transmembrane domain (ΔTM mutation), resulting in exon 6 skipping during mRNA production. Due to alternate splicing, a fraction of the mRNA produced by these alleles includes the transmembrane region but is missing the cytoplasmic region. The remaining two sequences differed only by synonymous substitutions. All of the exonic polymorphisms of KIR2DL4 could be detected by single‐stranded conformational polymorphism of individually amplified exons. The ΔTM mutation is in linkage disequilibrium with the killer cell immunoglobulin‐like receptor (KIR) A haplotype, and the wild‐type sequence is in linkage disequilibrium with the B haplotype. The frequencies of alleles with the ΔTM mutation or Ig‐domain polymorphisms did not differ between women who experienced pre‐eclampsia and normotensive controls. Similarly there was no difference in the KIR gene repertoire in pre‐eclampsia and normotensive controls.

Periodontal attachment loss is mediated by overproduction of tumour necrosis factor (TNF) and interleukin (IL)-1, and appears to have a genetic component. The 8.1 major histocompatibility complex (MHC) ancestral haplotype (HLA-A1,B8,TNFA-308(2),DR3) is associated with elevated TNF production and predisposes carriers to several autoimmune/immunopathological disorders, including rapid progression of HIV disease, but not early onset periodontal disease in healthy individuals. Rather a high proportion of subjects with severe periodontal disease carry allele 2 at IL-1A-889 and IL-1B+3953. We predicted that genetic associations may be different or clearer in HIV patients, as they often show elevated production of TNF and IL-1 and periodontal attachment loss. Hence periodontal parameters and IL-1 polymorphisms were assessed in HIV-positive subjects expressing HLA-B8 with or without other markers of the 8.1 haplotype. Of 16 HLA-B8 subjects, 13 demonstrated elevated probing pocket depth and clinical attachment loss. The difference was statistically significant and did not correlate with smoking, age, CD4 T-cell counts, HIV viral load or levels of dental plaque. As TNFA-308 (allele 2) was present in four non-B8 subjects who had minimal attachment loss, it may not mediate the effect of the 8.1 haplotype. Moreover, polymorphisms at IL-1A-889 and IL-1B+3953 did not significantly affect periodontal parameters. Thus a central MHC gene characteristic of the 8.1 haplotype was the clearest determinant of periodontal attachment loss in HIV-infected individuals.