Following short-term culture, Langerhans cells mature morphologically and functionally into potent immunostimulatory cells. As regulation of gene expression accompanies this maturation process, it is likely that differentially expressed genes are involved in the maturation events. Using the recently described method of differential display, we generated cDNA expression patterns starting with mRNA of murine epidermal Langerhans cells isolated either directly (fLC) or following 3 d cultivation (cLC). Five hundred putative differentially expressed cDNA fragments were recovered from the gel. For a part of the fragments differential expression was confirmed by dot blot and Southern hybridization procedures. These cDNA fragments were subcloned and sequenced following the verification step. Database searches revealed that unknown genes as well as already characterized genes were identified. A cDNA fragment preferentially hybridizing with fLC was identified as the murine surface marker 4F2 (CD98). Downregulation of the activation marker 4F2/CD98 was confirmed by additional analysis at the mRNA and protein level. The downregulation of 4F2 surface expression on cLC is compatible with the notion that the committed, terminally differentiated cLC downregulate proteins involved in proliferation and cell survival.