IgG subclass-dependent Recognition of Porphyromonas Gingivalis Antigens in the Early-onset Periodontitis

Abstract

Studies of the IgG subclass responses in earlyonset periodontitis(EOP) have frequently demonstrated elevated levels of total IgG or IgG2 to whole cell antigens, outer membrane proteins, and/or lipopolysaccharides(LPS) of Actinobacillus actinomycetemcomitans(Aa)1,2) or Porphyromonas gingivalis(Pg)3 according to the disease type. (Hammarstrom et al., 1986) IgG1, IgG3 and IgG4 antibodies are primarily reactive to protein antigens and IgG2 to bacterial carbohydrates, such as LPS or capsular polysaccharides(CPS). Moreover, each IgG subclass response has been studied in the context of the genetic control of an individual. Immunodominant antigens of Aa in localized juvenile periodontitis(LJP) were reported to include the 29-kd, 40-kd and 75-kd outer membrane proteins, and capsular carbohydrates(CPS) as well as LPS, while those of Pg in rapidly progressive periodontitis(RPP) were fimbriae, 75-kd protein, CPS, and LPS5). There have been controversies in regard to the bacterial antigens being recognized as immunodominant especially in the case of outer rnembrane proteins, presumably due to individual differences in IgG subclass responsiveness or to the complexities of the bacterial antigens. There has also been some debate regarding bacterial LPS or CPS in terms of their immunodominant nature in the pathogenesis of EOP. A previous investigation from our laboratory has focused on the various patterns of elevated IgG sunbclasses to Pg 381 in LJP or RPP patients6). To better understand the immunodominant antigens recognized by a panel of IgG subclass antibodies, we performed dot immunoblot analysis of selected bacterial antigens of Pg that are recognized by either a single or by various combinations of IgG subclasses in early-oneset periodontitis.