In the last decade, much attention has been devoted to study immunologic factors in early-onset periodontitis (EOP). This study was designed to investigate peripheral blood lymphocyte subpopulations cells in patients with EOP, 32 patients with EOP and 10 normal healthy control subjects were included in the study. Peripheral blood T-lymphocytes, helper T-cells, suppressor T-cells, B-lymphocytes, natural killer (NK) cells and the Th/Ts ratio were determined using appropriate monoclonal antibodies and the indirect immunofluorescence method. In the EOP group, T-lymphocytes and helper T-cells were found to be significantly lowere where as NK cells was significantly higher than the control group. They had normal numbers of B-lymphocytes, suppressor T-cells, and the Th/Ts ratio. These findings could contribute to the science about EOP in Indonesia, and to the immunopathogenesis of EOP
