EXTRACTS OF PERIODONTOPATHIC MICROORGANISMS LACK FUNCTIONAL SUPERANTIGENIC ACTIVITY FOR MURINE T-CELLS

Products of periodontopathic bacteria exert immunomodulatory effects o n various lymphoid cell populations, some of which have been implicate d in the pathogenesis of periodontitis. It has recently been suggested that some of these bacterial products may possess superantigenic (SAg ) activity. SAg bind simultaneously to the V-beta chain of T cell rece ptors and to class II major histocompatibility complex molecules, ther eby activating as many as 35% of T cells to proliferate and produce cy tokines. In order to examine this question, the proliferation of splen ic and thymic T cells from immunologically naive, 3-6-wk-old Balb/c (H -2(d)), C57BL/6 (H-2(b)) and C3H/HeJ (H-2(k)) mice was assessed in res ponse to sonic extracts of periodontopathogens. Laboratory and/or refe rence strains of a.o. Actinobacillus actinomycetemcomitans, Porphyromo nas gingivalis, Prevotella intermedia and Prevotella nigrescens were u sed as stimulants. Staphylococcal enterotoxin B (SEE), a known superan tigen, was utilized as a positive control. Unfractionated spleen cells responded to several of the tested preparations of the different bact eria, as well as to SEE, Con A and Escherichia coli LPS. Thymocytes re sponded to Con A and SEE, but not to LPS or to any sonic extract. Sple en cells depleted of B cells by panning responded to SEE and Con A, bu t not to LPS and showed a reduced response to sonicates. The residual response of B cell-depleted spleen cells was reduced essentially to ba ckground by treatment with anti-Thy 1.2 + C'. Similar results were obt ained in the presence of 5% added mitomycin-treated antigen presenting cells, indicating that these cells were not limiting. These results d emonstrate that extracts of periodontopathic bacteria do not stimulate murine T cells in a manner consistent with superantigenic activation.