[Personal identification from antibodies to oral streptococci using ELISA]

Serum antibodies to oral streptococci were titrated by ELISA for the purpose of personal identification. The bacteria concerned comprised 9 strains of Streptococcus mutans, which are known to cause dental caries, and one strain of Streptococcus sanguis commonly found in the oral cavity and harmless to the teeth. The quantities of IgM antibodies to these streptococci were more or less dependent on the total levels of serum IgM. However, no relation was found between the IgG antibodies and the total serum levels of IgG. IgA antibodies showed a degree of correlation that was intermediate between those of the IgM and IgG antibodies. Two antibodies, anti-Streptococcus mutans PS14 (anti-SM) and anti-Streptococcus sanguis 10556 (anti-SS), were selected, because the cross-reactivities of the IgG antibodies with these streptococci were slight. The quantity ratios of IgG anti-SM antibodies and IgG anti-SS antibodies differed from person to person, ranging from about 1:1 to 1:6 in 129 healthy Japanese adults. ELISA was considered to be appropriate for assaying these antibodies because of its good intra-assay reproducibility. The IgG anti-SM/anti-SS quantity ratio was not related to sex, age or ABO blood group, and appeared to be unrelated to the "decayed, missing and filled teeth index" (DMF index). The anti-SM/anti-SS ratios were investigated for 12 months after the preparation of bloodstains. They remained almost unchanged for 8 months, although the reactivities of individual IgG antibodies began to decrease 3 to 5 months after preparation. These results indicate that the ratio of IgG anti-streptococcal antibodies in bloodstains is a very useful parameter in personal identification.