Co-Culture of Human Keratinocytes on Post-Mitotic Human Dermal Fibroblast Feeder Cells: Production of Large Amounts of Interleukin 6

A large synthesis of human IL-6 was demonstrated in co-cultures of human keratinocytes on post-mitotic human dermal fibroblast (HDF) feeder layers. Immunoreactive IL-1β could be detected in the co-cultures and the addition of rabbit anti IL-1β antibodies to the co-cultures considerably reduced the IL-6 synthesis, suggesting that it was induced by endogenous IL-1β. Addition of saturating concentrations of IL-1β to HDF feeder layers as well as to subcultures of keratinocytes induced in both similar but moderate IL-6 production. Conditioned medium from keratinocyte cultures induced IL-6 secretion in HDF feeder cells, whereas the conditioned medium from HDF feeder layers led to only minimal increase of keratinocyte IL-6 production. The co-cultures of keratinocytes on HDF feeder layers produced much larger amounts of IL-6 than the sum of the IL-6 produced by the feeder cell and keratinocyte cultures after the addition of IL-1β. The co-cultures of keratinocytes with HDF feeder layers separated by a permeable membrane in a two-chamber system produced significantly lower amounts of IL-6 than the unseparated co-cultures. These findings indicate that a direct cell contact between keratinocytes and feeder cells is involved in the overproportioned increase of IL-6 production and secretion into the medium