1. T-lymphocytes are small white blood cells, whose main function is to enhance the reaction of other cells of the immune system-for example, b-lymphocytes and macrophages - to bacterial invasion.
2. T cells can produce substances called cytokines, such as interleukins (ILs), which stimulate the immune response. Cytokine is the General name for any protein that is secreted by cells and affects the behavior of neighboring cells. Cytokines, which play an important role in periodontitis include interleukin-1 (IL-1), interleukin-6 (Il-6), interleikina-8 (silt-8)and tumor necrosis factor-alpha (TNF-alpha).