Purpose: Gingiva-resident memory B cells found recently in healthy periodontal tissue may play important roles in maintaining homeostasis against bacterial plaque. Whether resident memory B cells exist in healthy peri-implant tissue and how they respond in peri-implantitis lesions are of interest. The aim of this study was to preliminarily investigate whether memory B cell activities are related to inflamed or healthy peri-implant status.
Materials and Methods: Patients with peri-implantitis or healed implants were recruited. The gingiva samples were collected and divided into inflamed (n = 4), treated (n = 4), and healed (n = 3) groups, followed by a flow cytometry analysis staining with CD3, CD19, CD27, CD38, and RANKL. The biopsy samples were also cryo-embedded for immunofluorescent double staining of CD19 and CD27.
Results: CD27+ CD38+ ASC comprised 83.3% ± 3.3% of the total B cells in the inflamed group, and this proportion in the treated group was reduced to 44.5% ± 13.4%. The proportion of CD27+ CD3+ T cells was found to be unchanged between the inflamed and treated groups. Immunofluorescent staining indicated that CD19+ CD27+ population infiltrated peri-implant connective tissue. RANKL was expressed by almost all B cells and a portion of T cells in the inflamed group, while the proportions of RANKL+ B and T cells were significantly reduced in the treated group. Barely any memory B cells were detected in the healed group.
Conclusion: Memory B cells were markedly activated in peri-implantitis and responded to the suprastructure removal treatment. The lack of gingiva-resident memory B cells in the clinically healed implants serves as a hint for the weakness of peri-implant tissue against bacterial plaque.