Identification of γδT lymphocytes in human periapical lesions

Abstract

Endodontic (root canal) therapy is required when the pulp of a tooth becomes necrotic due to a bacterial infection or trauma. A proportion of patients who receive endodontic therapy subsequently have periapical (around the tooth root) lesions detected by radiolucency. Currently, there are no means to identify susceptible patients. Although tissue from periapical lesions has been described as inflammatory, inflammatory cell types and their functions have been poorly characterized. For example, T lymphocytes were identified using pan specific anti‐CD3 mAb, which recognizes both αβ and γδT cells. Using the current model of γδT cells as immunoregulatory cells; γδT cells can mediate protective or destructive milieus. We postulated that patients who have a periapical lesion, as identified by radiographic bone loss, mount a γδT cell response. We collected specimens removed by surgery from both periapical lesions and other oral tissues, generated total RNA and performed reverse‐transcriptase polymerase chain reaction to identify rearranged δ genes. Results were confirmed with semi‐nested polymerase chain reaction. In addition, we demonstrate that these lesions contain a population of CD3+ cells that are αβT cell receptor negative, implying that these cells are γδT cells. Here we show that 36/37 of periapical lesions and only 2/11 of other lesions contain γδT cells (P < 0.0001). Vδ2+ T cells were the most common subtype identified (30/36) in these samples. This is the first report in the literature of the presence of γδT cells in human periapical lesions.