Relative proportions of T-cell subpopulations and cytokines that mediate and regulate the adaptive immune response in patients with aggressive periodontitis

Background: Both the virulence factors of periodontopathic bacteria and the immune response against them have been involved in tissue destruction observed in periodontal disease. Considering the regulatory role of cytokines produced by T cells, the purpose of this study was to compare the CD3⁺, CD4⁺, and CD8⁺ subpopulations of T cells, and to characterize the mRNA of cytokines involved in the adaptive immune response in a group of healthy/gingivitis 1 (HI/G1) individuals and aggressive periodontitis (AgP) patients. Methods: The percentages of T-cell subpopulations were analyzed in 10 gingival samples of HI/G1 individuals and 10 gingival samples of AgP patients by immunohistochemistry. The presence of interleukin (IL)-2, interferon (IFN)-γ, IL-4, IL-5, IL-10, IL-13, and transforming growth factor (TGF)-β was measured by reverse transcription polymerase chain reaction (RT-PCR) of mRNA extracted from complete gingival biopsies. Results: Significant differences were found in CD3⁺ and CD4⁺ cell counts between both groups. The parameters were lower in the gingival biopsies from AgP patients while CD8⁺ counts were similar in both groups. The cytokine mRNA analysis showed constant expression of IL-2 and IFN-γ in all cases. The mRNA of IL-5 and IL-10 was present in the majority of HI/G1 (N = 10, N = 9, respectively) but was not in the AgP group (N = 2, N = 1). IL-13 and TGF-β were only detected in HI/G1 (N = 2, N = 3) and IL-4 was not detected in any of the individuals. Conclusions: These results indicate that the role of the CD8⁺ subpopulation in aggressive periodontitis lesions is limited. On the other hand, cytokines IL-2 and IFN-γ may not be relevant in the progression of aggressive periodontitis.