title: Heterogeneity of antibodies reactive with the dominant antigen of Actinobacillus actinomycetemcomitans.
abstract: The serotype b-specific carbohydrate antigen (SbAg) of Actinobacillus actinomycetemcomitans Y4 is reported to be the O antigen of lipopolysaccharide, and the highest titers of serum antibody reactive with A. actinomycetemcomitans in early-onset periodontitis (EOP) patients bind SbAg. These high titers of serum antibody reactive with SbAg are associated with a lesser extent and severity of periodontal disease. The aim of this study was to determine if a limited number of genes code for anti-SbAg antibodies as has been shown for immunoglobulin G (IgG) reactive with the type b polysaccharide from Haemophilus influenzae. Serum IgG reactive with the SbAg was prepared from 20 high-titer EOP patients by affinity chromatography. The IgG subclass concentrations were determined, and heterogeneity was analyzed by isoelectric focusing (IEF). IgG2 was the dominant subclass (83% of total IgG) in the anti-SbAg IgG fraction and represented an average of 1.33% of total serum IgG2. The IgG2 reactive with SbAg was isolated from the affinity-purified IgG fraction by affinity chromatography with protein A and subclass-specific monoclonal antibodies. On IEF gels, only 4 to 20 bands were observed in the anti-SbAg IgG fractions, indicating limited heterogeneity. N-terminal amino acid sequence analysis of eight representative anti-SbAg IgG2 preparations indicated that variable heavy and light chains consisted largely of V(H)III and V(kappa)II, respectively. However, a significant fraction of anti-SbAg may use V(H) and V(lambda) genes with blocked N termini. In short, these findings indicate that IgG reactive with SbAg is very much like the antibody reactive with H. influenzae type b polysaccharide. Similarities include IgG2 dominance, limited bands on IEF gels, supporting an oligoclonal response, and use of genes from V(H)III and V(kappa)II regions.
authors.affiliation: Clinical Research Center for Periodontal Diseases, School of Dentistry, Medical College of Virginia, Virginia Commonwealth University, Richmond 23298, USA.
authors.forename: K
authors.initials: K
authors.lastname: Nakashima
authors.forename: H A
authors.initials: HA
authors.lastname: Schenkein
authors.forename: J V
authors.initials: JV
authors.lastname: Califano
authors.forename: J G
authors.initials: JG
authors.lastname: Tew
mesh_terms: D016976:Aggregatibacter actinomycetemcomitans / Q000276:immunology*; D000595:Amino Acid Sequence; D000907:Antibodies, Bacterial / Q000276:immunology*; D000915:Antibody Affinity; D000916:Antibody Diversity; D006801:Humans; D007074:Immunoglobulin G / Q000032:analysis; D007132:Immunoglobulin Isotypes / Q000032:analysis; D007145:Immunoglobulin kappa-Chains / Q000032:analysis; D007146:Immunoglobulin lambda-Chains / Q000032:analysis; D007526:Isoelectric Point; D008969:Molecular Sequence Data
chemical_list: D000907:Antibodies, Bacterial; D007074:Immunoglobulin G; D007132:Immunoglobulin Isotypes; D007145:Immunoglobulin kappa-Chains; D007146:Immunoglobulin lambda-Chains