When evaluating immune cell infiltration in periodontitis, we discovered unique patterns related to the expression levels of CD27, notably positive correlations with the infiltration of activated CD4 memory T cells and plasma cells, while negative correlations were observed with the levels of resting mast cells, eosinophils, M2 macrophages, CD8 T cells, and monocytes, among others. The gene discussed is CD27; the disease is periodontitis.