HETEROGENEOUS EXPRESSION AND RELEASE OF CD14 BY HUMAN GINGIVAL FIBROBLASTS - CHARACTERIZATION AND CD14-MEDIATED INTERLEUKIN-8 SECRETION IN RESPONSE TO LIPOPOLYSACCHARIDE

To identify the role in periodontal inflammatory diseases of human gin gival fibroblasts (HGF), the major constituents of gingival tissue, th e expression of CD14, a possible lipopolysaccharide (LPS) receptor, an d the release of soluble CD14 (sCD14) by HGF were examined. Among the HGF samples from the nine donors tested, more than 50% of the HGF from five donors expressed CD14 but less than 20% of HGF from the other fo ur donors did so, as determined by how cytometric analysis. The CD14 e xpression on the cell surface was correlated with the expression of CD 14 mRNA, The HGF and skin and lung fibroblasts tested expressed no CD1 8, which indicates that fibroblasts do not possess other LPS receptors , such as CD11b/CD18 and CD11c/CD18. The CD14 expression by the HGF wa s decreased after subculturing and was highest at the confluent stage of culture. The treatment of high-CD14-expressing (CD14(high)) HGF wit h phosphatidylinositol-phospholipase C reduced CD14 expression; this r esult and the increase in a 55-kDa CD14 indicate that the membrane CD1 4 (mCD14) on the HGF may be a 55-kDa glycosylphosphatidylinositol-anch ored protein. CD14(high) HGF spontaneously released 48- and 57-kDa sCD 14, The total release of sCD14 by the HGF was augmented by gamma inter feron and Escherichia coli LPS in accordance with the increased expres sion of mCD14, The CD14(high) HGF secreted interleukin-8 in response t o LPS, and the secretion was completely inhibited by anti-CD14 antibod y, These results suggest that (i) HGF consist of populations that are heterogeneous on the basis of different levels of expression of CD14 a nd (ii) CD14(high) HGF secrete inflammatory cytokines in response to L PS via CD14.