Endogenous IL-15 Sustains Recruitment of IL-2Rβ and Common γ and IL-2-Mediated Chemokine Production in Normal and Inflamed Human Gingival Fibroblasts

Abstract

We recently reported that anti-IL-15 neutralizing mAb has been shown to inhibit production of MCP-1 in response to IL-2 from normal human gingival fibroblasts (HGF), the major constituent of gingival tissue. In the present study, we examined the expression of IL-2R and IL-15R subunits in HGF from normal and inflamed regions and the role of endogenous IL-15 in IL-2-mediated signaling. Normal HGF expressed IL-2Rβ and common γ-chain (γc) but not IL-2Rα or IL-15Rα, whereas inflamed HGF expressed IL-2Rα, IL-15Rα, IL-2Rβ, and γc, as assessed by RT-PCR and flow cytometry. Exogenous IL-2 and IL-15 induced production of MCP-1 but not IL-8 in normal HGF, and induced the production of both chemokines in inflamed HGF. Both HGF constitutively transcribed the 48 aa-IL-15 isoform, and the isoform was not actively secreted but rather existed as a membrane-bound form. Pretreatment with anti-IL-15 neutralizing mAb for 24 h completely inhibited the production of MCP-1 induced by IL-2 and IL-15 and IL-2-induced phosphorylation of Jak 1 and 3 in HGF. The pretreatment and RNA interference targeted to IL-15 mRNA resulted in total inhibition of the IL-2Rβ and γc expression at mRNA and protein levels. Furthermore, excess amounts of IL-2 restored the inhibitory effect of anti-IL-15, inhibition of NF-κB abrogated the expression of IL-2Rβ and γc, and IL-2-induced-nuclear translocation of NF-κB was completely inhibited by the RNA interference in HGF. These results suggest that endogenous membrane-bound IL-15 sustains recruitment of IL-2Rβ and γc through activation of NF-κB in HGF.

Expression of interleukin-15 and its receptor on the surface of stimulated human umbilical vein endothelial cells

“…Membrane-bound endogenous IL-15 sustains recruitment of IL-2Rβ and γ through NF-κB in human gingival fibroblasts [33] . Murine dendritic cells require IL-15α to present IL-15 in trans to natural killer cells during natural killer cell priming [34] .…”

Histamine Amplifies Immune Response of Gingival Fibroblasts

“…Human gingival fibroblasts, the major constituent of gingival connective tissue, are heterogeneous (Lekic et al, 1997;Sugawara et al, 1998) and express immunological receptors (Rs), such as IL-1R (Kanda-Nakamura et al, 1996), IL-2R (Ozawa et al, 2004), TNFR (Butler et al, 1994), CD14 (Watanabe et al, 1996;Sugawara et al, 1998), and Toll-like receptors (Tamai et al, 2002). Stimulation of gingival fibroblasts with these cytokines and LPS induces the production of various cytokines, such as IL-1, IL-6, and IL-8 (Takada et al, 1991;Watanabe et al, 1996;Sakuta et al, 1998;Sugawara et al, 1998;Tamai et al, 2002;Ozawa et al, 2004).…”

Endogenous membrane-bound IL-15 sustains recruitment of IL-2Rβ and common γ through activation of NF-κB in human gingival fibroblasts

“…Reverse transcriptase-polymerase chain reaction (RT-PCR), flow cytometry, enzymelinked immunosorbent assay (ELISA), Janus tyrosine kinase (JAK) phosphorylation, RNA interference (RNAi), and immunostaining were performed as described [9,10].…”

“…The T cell features in diseased periodontal tissues can be compared with those in rheumatoid arthritis. These observations led us to investigate (1) whether HGF from normal and inflamed regions differentially express IL-2R and IL-15R subunits and respond to IL-2 and IL-15 and (2) the role of endogenous IL-15 in IL-2-mediated signaling [9,10].…”