Expression of IL-2 receptor β and γ chains by human gingival fibroblasts and up-regulation of adhesion to neutrophils in response to IL-2

To investigate the role of human gingival fibroblasts (HGF), the major constituents of gingival tissue in periodontal inflammatory disease, the expression of interleukin-2 receptor (IL-2R) α, β, and γ chains was examined. Immunohistochemistry showed a pronounced accumulation of CD8⁺ T cells in the inflamed lamina propria of gingival tissue from patients with adult periodontitis. HGF express IL-2Rβ and IL-2Rγ at mRNA and protein levels, but the expression of IL-2Rα could not be detected, as assessed by reverse transcriptase-polymerase chain reaction and flow cytometry. IL-2Rβ, and -γ expressed on HGF were functionally active, as addition of neutralizing anti-IL-2Rβ and -γ antibodies caused inhibition of the IL-2-induced production of monocyte chemoattractant protein-1 (MCP-1), and addition of IL-2 induced phosphorylation of Janus tyrosine kinase 3, which is critical in signaling through IL-2Rγ in HGF. The IL-2-induced MCP-1 production was significantly inhibited by pretreatment with neutralizing antibody to IL-15. Addition of IL-2 also induced a marked up-regulation of the expression of intercellular adhesion molecule-1 (ICAM-1) on the surface of HGF, which in turn, significantly augmented the adhesion of human neutrophils, which were inhibited by an anti-ICAM-1 antibody. These results suggest that HGF express functional IL-2Rβγ, respond to IL-2 from infiltrated T cells, and actively participate in the inflammatory process in the periodontal region and that IL-15 produced by HGF sustains IL-2-mediated signaling in HGF.