Limit dilution analysis of peripheral blood T lymphocytes specific to periodontopathic bacteria

Limit dilution analysis (LDA) was used to determine the presence and frequency of periodontopathic-bacteria-specific T cells in the peripheral blood of patients with chronic inflammatory periodontal disease. Twelve adult periodontitis (AP), 13 marginal gingivitis (MG) and 12 healthy control subjects took part in the study. Bacteroides gingivalis and Actinomyces viscosus were used as test organisms, while tetanus toxoid was used as the control antigen. The median PTL-p frequencies to B. gingivalis were 46.33 x 10(-6), 45.33 x 10(-6) and 58.83 x 10(-6) in the control, gingivitis and AP groups respectively, while the median PTL-p frequencies to A. viscosus were 13.8 x 10(-6), 17.33 x 10(-6) and 11.5 x 10(-6), again in the control, gingivitis and AP groups. There were no statistically significant differences between the groups. All subjects displayed 'single-hit' kinetics with the control tetanus toxoid antigen and, with three exceptions, 'single-hit' kinetics was also found with the two test organisms. One control subject displayed a 'saw-tooth' curve with A. viscosus and a 'suppressor' curve with B. gingivalis, while two MG subjects had a 'saw-tooth' curve with B. gingivalis. These complex curves suggest that, in some subjects, more than one limiting cell type may exist in the cultures. Nevertheless, the results of the present study illustrate that lymphocytes specific to periodontopathic bacteria exist in the peripheral blood of both diseased and non-diseased subjects.