Interleukin-1 modulates T6 expression on a putative intra-epithelial Langerhans cell precursor population

Langerin+ versus CD1a+ Langerhans cells in human gingival tissue: a comparative and quantitative immunohistochemical study

Langerhans cells (LC) are dendritic cells of the immune system able to capture intraepithelial pathogens and migrate to regional lymph nodes to present them to naive T cells. Up to now immunohistological studies on human gingival LC have been carried out using antibodies against HLA-DR or CD1a molecules. A new marker of LC called Langerin (CD207) and described, among other subcellular localisations, in the Birbeck granules is now available in immunohistochemistry. The purpose of this in situ study was to quantify and to compare Langerin+ versus CD1a+ LC number in order to show differences in the expression of these molecules, if any, and to determine which marker is the most specific. The present study was conducted using nine frozen healthy gingival samples. Double immunofluorescence procedures were performed with an anti-Langerin antibody revealed by FITC and with an anti-CD1a-PE antibody. Mounted slides were analysed by fluorescence microscopy and quantifications were performed on projected slides associated with a grid of 0.015 mm(2). Our results have shown that 1/ the number of CD1a+ LC was significantly increased (P=0.01) when compared with Langerin+ LC 2/ 92% of Langerin+ LC co-expressed CD1a 3/ only 82% of CD1a+ cells co-expressed Langerin 4/ a positive correlation was noted between CD1a+ and Langerin+ LC numbers. The present study has revealed the heterogeneity in the phenotype of gingival LC population and shown that Langerin seems the most specific marker for the study of LC.

Expression of CD1a monocytes cultured with supernatants from periodontally diseased gingival epithelial cells

Langerhans cells are believed to originate from the monocyte lineage and have been reported to increase in number with plaque accumulation and gingival inflammation. The aim of this study was to investigate the effects of local gingival epithelial factors on the induction of CD1a, a Langerhans cell phenotype, on monocyte rich populations.

MATERIALS AND METHODS

Peripheral blood monocyte rich in populations from healthy subjects were cultured for 24 h with either healthy gingival or periodontally diseased gingival epithelial supernatants. Additionally, the monocyte rich populations were cultured with cytokines IL-I alpha, IL-I beta, IL-6 and TNF-alpha which are known to be produced by epithelial cells or co-cultured with autologous epithelial cells. The per cent CD1a positive cells was determined using FACS analysis.

RESULTS

Healthy gingival supernatants did not induce CD1a expression in monocyte rich populations, however, a significant increase in per cent CD1a+ cells for monocyte rich populations cultured with five (P < 0.01) of six periodontal gingival epithelial supernatants was found. IL-I alpha or TNF-alpha (10 ng/well) resulted in a significant increase in the per cent CD1a+ cells (P < 0.01). Depletion of CD1a+ Langerhans cells from healthy gingival epithelium did not enhance induction of CD1a expression in monocyte rich populations. Monocyte rich populations cultured together with non-depleted epithelial cultures resulted in a decreased per cent of CD1a+ cells.

CONCLUSION

These findings indicated that epithelial factor/s associated with periodontally involved epithelia, may be involved in inducing a Langerhans cell phenotype in monocyte rich populations. The data also provide indirect evidence for a role of Langerhans cells in inhibiting induction of CD1a in healthy epithelium.

Reconstitution of cutaneous neural-immunological networks following bone marrow transplantation

During allogeneic bone marrow transplantation (BMT), host epidermal Langerhans cells (LC) are depleted and replaced by LC derived from the bone marrow inoculum. LC have recently been shown to form intimate spatial associations with intraepithelial nerves (IEN), which release regulatory peptides. The present study investigated whether the IEN network within skin remains intact during BMT, and whether repopulating LC re-established contacts with IEN. Double-labeling immunohistochemical techniques were employed using antibodies to CD1a and neural cell adhesion molecule (CD56) to identify LC and IEN, respectively. LC were depleted by conditioning for BMT, and repopulating LC reached normal values after day +100. In contrast to fluctuations in the LC network, the frequency of IEN remained unchanged during the post-BMT period. Contacts between LC and IEN were present both before and after BMT, and repopulating LC established a spatial interaction with IEN similar to that seen before BMT. These data provide the first evidence for the dynamic nature of the spatial relationship of LC with IEN, and raise intriguing questions regarding the mechanisms that direct homing of LC within epithelia.

Immunohistochemical analysis of effects of cyclosporin A on gingival epithelium

Cyclosporin A (CSA)-induced gingival overgrowth was immunohistochemically compared with that phenytoin-induced and nonspecific inflammatory gingiva, and CSA concentration was determined for dental plaque. Leu-6+ epithelial dendric cells (EDC) were found to significantly decrease in number in CSA-induced gingival overgrowth, while the ratio of HLA-DR+ EDC to Leu-6+ EDC did not change significantly. The expression of class II major histocompatibility complex antigens, such as HLA-DR, -DP and -DQ on keratinocytes did not change by CSA-treatment. Leu-4+ mononuclear cells in CSA-induced gingival overgrowth were located primarily in the connective tissue far outside the epithelium. CSA concentration was much higher in dental plaque than in blood and other tissues. Immune response thus appears to be suppressed in the epithelial layer of CSA-induced gingival overgrowth through decrease in Leu-6+ HLA-DR+ EDC and T cell infiltration, both due to CSA in dental plaque. DNA polymerase alpha was detected in much fewer basal keratinocytes of CSA- and phenytoin-induced gingival overgrowth. Epithelial hyperplasia may thus be not due to increased keratinocyte proliferation, but rather to enhanced keratinocyte life span.

Modulation of Langerhans cell surface antigen expression by recombinant cytokines

This study examined the influence of cytokines on surface antigen expression by gingival Langerhans cells (LC) in organ culture, interleukin-6 (IL-6) and tumor necrosis factor alpha (TNF-alpha) upregulated the expression of CD1a, HLA-DR and HLA-DP antigens on LC. TNF-alpha, interleukin-4 (IL-4), and transforming growth factor beta (TGF-beta) suppressed CD29 expression, while other cytokines, including interleukin-3 and granulocyte-macrophage colony stimulating factor, were without effect. No cytokines induced CD3, CD4, CD23, CD25 or CD45 RA antigen expression in organ culture. Since TNF-alpha and IL-6 can be secreted by keratinocytes, these molecules, together with interleukin-1, are likely to play a role in the local control of LC number and function within the epithelial milleu. Thus, alterations in cytokine secretion by keratinocytes may at least in part be responsible for variations in LC number and antigen expression which occur in oral mucosal disorders.

Partial characterization of an interleukin-1-like factor in human gingival crevicular fluid from patients with chronic inflammatory periodontal disease

A significant level of interleukin-1-(IL-1)-like activity was detected in gingival crevicular fluid obtained from sites in patients with chronic inflammatory periodontal disease, confirming a previous report of IL-1-like activity detected in human gingival crevicular fluid from patients with chronic inflammatory periodontitis (J. A. Charon, T. A. Luger, S. E. Mergenhagen, and J. J. Oppenheim, Infect. Immun. 38:1190-1195, 1982). In the present study, we sought to investigate whether this IL-1-like activity belonged to IL-1 alpha or IL-1 beta and to characterize some of the biochemical properties of this factor. Polyclonal antibodies against recombinant human IL-1 alpha or IL-1 beta (rIL-1 alpha or rIL-1 beta) have been used for serological comparison of the IL-1-like factor. IL-1-like activity was completely neutralized by anti-human rIL-1 alpha antiserum, but not by anti-human rIL-1 beta antiserum. On gel filtration with a high-pressure liquid chromatographic Superose 12 column, IL-1-like activity was separated into two peaks, one with a molecular weight of about 43,000 and the other with a molecular weight of less than 17,000. The majority of the IL-1-like factor with a low molecular weight in human gingival crevicular fluid migrated at a molecular weight of about 17,000 under the reducing conditions of sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The specificity of the IL-1-like factor was further confirmed by an immunochemical method (Western blotting [immunoblotting]) by using anti-human rIL-1 alpha monoclonal antibodies. On isoelectric chromatography with a high-pressure liquid chromatographic Mono P column, the pI of this IL-1-like factor was between pH 4.9 and 5.2. These results suggest that the IL-1-like factor in human gingival crevicular fluid from diseased sites in patients with chronic inflammatory periodontitis consists predominantly of IL-1 alpha.

Interleukin 1 induces CD1 antigen expression on human gingival epithelial cells

The CD1 (T6) antigen is a highly specific marker for human Langerhans cells (LC). Previous studies have demonstrated that crude preparations containing murine interleukin-1 (IL-1) or a human epithelial cell-derived IL-1 inhibitor (ILS) modulate CD1 expression by LC in organ culture. This study examined the effect of organ-culture derived human IL-1, recombinant human IL-1, and purified ILS on CD1 expression in dispersed epithelial cell cultures. Both IL-1 preparations stimulated CD1 expression in whole and CD1-depleted cultures. The optimal dose level for this effect was 0.5 U/ml. Higher dose levels did not result in an increase in CD1 expression, implying that a limited pool of CD1 negative EC are induced to express CD1 by IL-1. Induction of CD1 expression on whole and depleted EC was abrogated by ILS. These results indicate that human IL-1 and an IL-1 inhibitor act in combination to modulate CD1 expression on Langerhans cells in the gingival epithelium.

The regulation of Langerhans cell T6, DR and DQ antigen expression: an hypothesis

A hypothetical model of the maturation pathway of Langerhans cells (LC) within an epithelial environment is presented. This model is based on in vitro studies using human gingival organ culture. In this model, T6 (CD1) antigen is induced on a T6(-) intraepithelial population by Interleukin-1 secreted by epithelial cells. This process is abrogated by a locally produced Interleukin-1 inhibitor, ILS. These T6(+) LC then express first HLA-DR and subsequently HLA-DQ surface antigens under the influence of either lipopolysaccharide or gamma interferon. The induction of these Class II antigens on LC is inhibited by prostaglandin E2. It is postulated that these Class II antigen positive LC are then available to function as antigen presenting cells. This hypothesis is consistent with in vitro studies and several in vivo observations. The basis of the hypothesis is the demonstration that locally produced factors may exert an influence on LC behaviour within an epithelial environment.

In vitro modulation of T6 expression on gingival Langerhans cells by interleukin-1 inhibitors and ETAF

T6 antigen is a highly specific marker for human Langerhans cells (LC). Previous studies have demonstrated that Interleukin-1 (IL-1) and an IL-1 inhibitor (ILS) modulate LC T6 expression (T6E) in explant culture. The present study examined the in vitro modulation of T6E by two molecules: epidermal-cell-derived thymocyte-activating factor (ETAF), and a bone-derived protein (BP) implicated in the control of bone homeostasis. The effect of purified ILS was also examined. ETAF mimicked the stimulatory effect of IL-1 on LC T6E, while BP depressed T6E in a manner resembling that seen with ILS. No agents altered Class II (DR and DQ) expression by LC. BP was a specific IL-1 inhibitor, and did not inhibit thymocyte proliferation in the standard IL-1 bioassay in the absence of IL-1. These results demonstrate that molecules resembling IL-1 or ILS can modulate T6E, and implicate locally produced ETAF and ILS in the regulation of T6E in the oral mucosa in vivo.