Previous studies in humans and experimental animals have provided evidence that antigen-specific T cells play a regulatory role in periodontal disease. However, little is still known regarding the properties to the T cell subpopulation(s) involved in regulating oral health or inflammation and periodontal bone loss, i.e., periodontal disease. The overall objective of the proposed reseach is to investigate T cell regulatory mechanisms which may be involved in local tissue inflammation and subsequent bone loss associated with periodontal disease. The studies will employ an experimental rat model and will specifically involve the isolation, generation and characterization of T cell clones which specifically help responses to the periodontopathogen Bacteroides gingivalis. The ability of these cloned T helper (Th) cells to regulate isotype-specific B cell growth and differentiation and to produce factors which mediate tissue destruction and repair will be evaluated. In addition, the influence of antigen-presenting cells in mediating T cell effects, and the ability of these cloned Th cells to influence periodontal bone loss in an experimental rat model will be determined.