IMMUNOGLOBULIN ALLOTYPES AND IMMUNOGLOBULIN-G SUBCLASS RESPONSES TO ACTINOBACILLUS-ACTINOMYCETEMCOMITANS AND PORPHYROMONAS-GINGIVALIS IN EARLY-ONSET PERIODONTITIS

The present study was performed to estimate the observed frequencies o f the immunoglobulin heavy-chain (Gm) and light-chain (Km) allotypes a mong patients with early-onset periodontitis (EOP) and their effect on the IgG2 subclass responses against Actinobacillus actinomycetemcomit ans Y4 and Porphyromonas gingivalis 381, respectively. Sixty-nine EOP patients, including 11 with localized juvenile periodontitis (LJP), 19 who had LJP, 15 with LJP-rapidly progressing periodontitis (RPP), and 24 with RPP, were examined for the Gm and Km allotypes by a hemagglut ination inhibition test, Levels of immunoglobulin G2 (IgG2) antibodies against the two organisms were determined by enzyme-linked immunosorb ent assay. Fifty race- and age-matched, periodontally healthy subjects were also included as a control group. The observed frequencies of th e Gm haplotype afnb and Km(1) were significantly higher in the RPP and LJP groups, respectively. The G2m(n)+ group of those with RPP and the Km(1)+ group of those with LJP had significantly higher levels of IgG 2 antibodies to A. actinomycetemcomitans and P. gingivalis, respective ly, The results indicate that linkage disequilibrium of the G2m(n) loc us in RPP patients or the Km(1) locus in LJP patients may be associate d with high IgG2 antibody responses to the respective bacteria. It was reasoned that the IgG2 antibody responses are associated with the imm unoglobulin allotypes. The function of IgG2 antibodies in their reacti on to different bacterial antigens maybe interpreted as either protect ive or nonprotective in the two different types of EOP (i.e., LJP and RPP).