GRANULOCYTE/MACROPHAGE COLONY-STIMULATING MATURATION OF MURINE EPIDERMAL LANGERHANS CELLS INTO POTENT IMMUNOSTIMULATORY DENDRITIC CELLS

Freshly isolated, murine epidermal Langerhans cells (LC) are weak accessory cells for primary T cell-dependent immune responses, but increase their stimulatory capacity at least 20-fold progressively over a 3-d culture with keratinocytes. We have studied the mediators of LC maturation. LC enriched from 12-h epidermal cultures by negative selection do not survive when cultured for 60 h in standard medium. LC survive and show increased stimulatory capacity for oxidative mitogenesis and the primary MLR when 30% keratinocyte-conditioned medium is included. Of the three cytokines that are known to be produced by keratinocytes, only granulocyte/macrophage CSF (GM-CSF) maintains viability and increases stimulatory capacity. IL-1 alone does not keep LC alive, but further enhances the stimulatory activity when combine…