Expression of Epidermal Differentiation Antigens in Cultures of Interspecific Somatic Hybrids (Human Keratinocytes × Mouse Fibroblasts 3T3–4E)

Interspecific somatic hybrids have been prepared by fusion of human epidermal cells with mouse fibroblasts 3T3–4E using PEG 4000. Expression of epidermal differentiation antigens (bullous pemphigoid antigens, BP, keratin subsets 55–57 k and 67 k), markers of basal and suprabasal cells, were studied by immunocytochemistry for 10 passages. These markers were detected in the hybrids early after fusion, indicating that cells from both compartments were able to fuse with 3T3–4E cells. However, the hybrids expressing high molecular weight keratins were no longer detected after 7 days in primary cultures and serial passages, whereas those expressing BP antigens and vimentin persisted. Low molecular weight keratins 52 K and 50 K were detected by SDS-PAGE at the second passage in precipitates formed between labeled hybrid lysates and total keratin rabbit antiserum. Karyo-type analysis showed mainly murine chromosomes and a submetacentric human chromosome between the 6th and the 10th passage.