In situ demonstration of natural killer (NK) cells in human gingival tissue

Recent studies have raised the possibility that natural killer (NK) cell activity may play a role in tissue destruction in chronic inflammatory periodontal disease (CIPD). This study aimed to locate and identify these cells in healthy and diseased gingival tissue. Leu 4, Leu 7, and Leu 11 monoclonal antibodies were used to characterize lesions of CIPD and to identify NK cells. Gingival tissue from three patient groups was examined. Group 1 subjects participated in a 21-day experimental gingivitis study. Group 2 subjects were children aged less than 8 years who had gingivitis associated with deciduous teeth. Group 3 consisted of patients with CIPD undergoing periodontal surgery. In group 1, NK cells were absent in health (Day 0) and gradually increased in number with increasing inflammation up to Day 21. The number and distribution of NK cells in Group 2 subjects resembled those seen after a 21-day experimental gingivitis study. In Group 3 subjects, lesions of CIPD which contained greater than 90% Leu 4+ cells ("T cell" lesions) contained few Leu 7+ cells and no Leu 11+ cells. The greatest number of NK cells were found in the "B cell" lesions (less than 60% Leu 4+ cells). The absence of NK cells in gingival health and their presence in diseased gingiva suggests that these cells are involved in the immune response to the accumulation of plaque.