Oral keratinocytes derived from the peritonsillar mucosa express the proinflammatory cytokine IL-6 without prior stimulation.

The aim of the present study is to examine the cytokine expression and corresponding receptor pattern of human oral mucosa-derived keratinocytes. The mRNA expression of these cytokines from isolated and purified cells was measured by a RT-PCR method, the protein production by ELISA, and the receptor expression was determined by FACS analysis. In freshly isolated oral keratinocytes, IL-1alpha, IL-1alpha receptor antagonist, IL-6, IL-8, TGF-beta, TNF-alpha, and bFGF were detectable at the protein and mRNA level, whereas PDGF and TGF-alpha were found only at the mRNA level. There were no detectable signals for IL-2 and IL-4. The cytokine production at the protein level was independent from stimulation with PMA (phorbol myristate acetate). Unstimulated commercially available and primary isolated epidermal keratinocytes showed similar cytokine pattern except a lack of IL-6. FACS analysis revealed receptor expression on oral keratinocytes for IL-1, IL-2, IL-4, IL-6, EGF, IFN-gamma, and PDGF. In addition, receptor mRNA for IL-8, TNF-alpha, FGF-2 and KGF could be detected, but not for IL-10. Our results show that human oral keratinocytes produce a cytokine panel comparable to epidermal keratinocytes. In contrast to the epidermis, IL-6 was produced by human oral keratinocytes constitutively without prior stimulation, which may indicate their active regulation role in the maintenance of the oral mucosa.