CD8A and ulcer disease: The ulcer epithelium in the periodontal pocket allows bacteria and their by‐products to enter the circulation, activating the immune system and leading to increased infiltration of activated T cells such as CD4+T cells (especially Th1 and Th17 cells), immunosenescent (CD57+CD28null) CD8+T cells, and CD8+CD38+T cells in the blood.