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

OBJECTIVE: 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 CDla, a Langerhans cell phenotype, on monocyte rich populations.
MATERIALS AND METHODS: Peripheral blood monocyte rich 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-Iα, IL-Iβ, IL-6 and TNF-α which are known to be produced by epithelial cells or co-cultured with autologous epithelial cells. The percent CDIa positive cells was determined using FACS analysis.
RESULTS: Healthy gingival supernatants did not induce CDIa expression in monocyte rich populations, however, a significant increase in per cent CDla⁺ cells for monocyte rich populations cultured with five (P < 0.01) of six periodontal gingival epithelial supernatants was found. IL-lα or TNF-α (10ng/well) resulted in a significant increase in the per cent CDla⁺ cells (P < 0.01). Depletion of CDla⁺ Langerhans cells from healthy gingival epithelium did not enhance induction of CDIa expression in monocyte rich populations. Monocyte rich populations cultured together with non-depleted epithelial cultures resulted in a decreased percent of CDla⁺ 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 CDIa in healthy epithelium.