Methods: Novel monoclonal antibodies were developed to locate periodontal pathogens P. gingivalis, T. forsythia and P. intermedia. Specificity and cross reactivity was confirmed using rat liver sections infected with 36 species of common cell and pathogenic bacteria frequently present in the human body. Eleven gingival granulation tissue samples were collected during periodontal surgery, from patients with chronic periodontitis who had undergone one round of initial periodontal therapy. Tissues were immediately fixed in 10% buffered neutral formalin for duration of 4 hours and paraffin embedded. Two sets of 2 μm thick tissue sections were used for Immunohistochemistry from each sample since two different antigen blocking solutions (horse serum and serum free protein block) were used. Results: Results using horse serum as antigen block correlated with the results of serum free protein block. From the eleven samples, 8 were positive for P.gingivalis, 10 for T. forsythia and 10 for P. intermedia within plaque surrounding the tissue edges in both sets of samples. Out of the positive samples 3 cases were positive intra-cellularly for P. gingivalis, 5 cases for T. forsythia and 2 for P. intermedia.
Conclusion: The produced monoclonal antibodies could be used as specific tools to visualize Porphyromonas gingivalis, Tannerella forsythia and Prevotella intermedia in human tissues. Also these bacteria may exist intra-cellularly in gingival tissues.