Polymorphisms of the mannose-binding lectin gene MBL in periodontitis in patients with Down syndrome

Periodontitis is considered to be a multifactorial and lifestylerelated dental disease. In Down syndrome, the onset of periodontitis starts from an early age, and appears to be a proper phenomenon of this syndrome. One possibility is that this phenomenon relates to the immune system of individuals with Down syndrome, yet little is known about the etiology, particularly the genetic factors. Mannose-binding lectin (MBL) is an important host factor of the innate immune system and may play a role in the defense against invading microorganisms in periodontitis. Here, we investigate the distribution of single nucleotide polymorphisms (SNPs) in the MBL gene at codons 52, 54, and 57 in both subjects with or without Down syndrome, with or without periodontitis. The subjects of this study from a Japanese population were: group (i) 10 individuals without Down syndrome without periodontitis; group (ii) 18 individuals without Down syndrome with periodontitis; group (iii) 12 individuals with Down syndrome without periodontitis; and group (iv) 20 individuals with Down syndrome with periodontitis. We carried out polymerase chain reaction-restriction fragment length polymorphism (PCRRFLP) using DNA from lingual mucosal cells of subjects, and determined the genotypes of all subjects. We found no different distributions of SNPs in the MBL gene at codons 52, 54, and 57 in subjects with or without Down syndrome, with or without periodontitis. These findings suggest that frequent abnormalities of the immune system in Down syndrome are dependent on the genetic background of the individual.