The purpose of this study was to evaluate the genotypic characterization of Actinobacillus actinomycetemcomitans (A. actinomycetemcomitans) using arbitrarily primed polymerase chain reaction (AP-PCR), to investigate the cytotoxicity of both clinical isolates and standard strains of A. actinomycetemcomitans for the human Jurkat T cells, and to measure the osteoclastogenic cytokines released by Jurkat cells infected with these bacterial strains. The random sequence primer 15 and 16 could distinguish different AP-PCR profiles between clinical isolates of A. actinomycetemcomitans. A. actinomycetemcomitans significantly suppressed Jurkat cell viability in time dependent fashion and the results of DNA fragmentation assay indicated that this bacterial species induced apoptosis in Jurkat cells undergoing apoptosis released the osteoclastogenic cytokine, IL-1$eta$, IL-6, TNF-$alpha$. These data support the hypothesis that induction of apoptosis is at least one essential step in A. actinomycetemcomitans induced local immunosuppressive pathway, and that A. actinomycetemcomitans can modulate the immunomodulatory cell population in the periodontal tissue by inducing T cell death through apoptosis, and that apoptosis of local resident T cells may play an active role in bone resorption by releasing osteoclastogenic cytokines, e.g. IL-1$eta$, IL-6, TNF-$alpha$.