Lymphocyte numbers and function in relation to periodontitis and smoking

Background: T and B lymphocytes play important roles in periodontitis. Smoking is considered a risk factor for periodontitis and may exert its negative effects through leukocytes. Taking smoking into consideration, the aim of this study was to analyze numbers of circulating T (CD3(+)) cells and their CD4(+) and CD8(+) subpopulations, B (CD19(+)) cells, and T-cell proliferative capacity in periodontitis. Methods: Lymphocyte immunophenotyping for T cells, their CD4(+) and CD8(+) subsets, and B cells was performed on peripheral blood from 76 periodontitis patients and 36 controls. Proliferative capacity of T cells was determined in whole-blood lymphocyte culture assays after mitogenic stimulation. Results: Total T cells, CD4(+) and CD8(+) subpopulations, and responsiveness to specific T-cell stimuli did not differ between patients and controls; in addition, B cells were not significantly elevated in periodontitis patients. However, more periodontal breakdown in smoking patients was associated with higher numbers of CD3(+) T cells, as well as with CD4(+) and CD8(+) T-cell subsets, and increased T-cell proliferation. Numbers of B cells were not affected by smoking. Conclusions: The increased numbers of T-cells and elevated T-cell responsiveness in patients who smoke may be one of several explanations why smoking is a risk factor for periodontitis. The mechanism of how T-cell function contributes to increase the severity of periodontal breakdown in smoking periodontitis patients needs to be investigated further.