Onco-embryonic antigens on murine normal adult cells.

Normal adult C57BL/6J fibroblasts, cultured to saturation density and therefore in resting phase, were harvested by EDTA, treated with trypsin at various concentrations for different lengths of time and then tested for absorbing capacity of a C57BL/He anti-embryo serum, the residual cytotoxic activity being measured by a 51Cr release assay on a C57BL/He lymphosarcoma known to carry embryonic antigens. A weak proteolytic treatment (0.05-0.25% trypsin for 5-10 min) uncovered structures which absorbed over 40% activity of the anti-embryo serum. The treated fibroblasts partially retained the absorbing capacity for an antihistocompatibility serum. Higher doses or longer exposure to trypsin progressively inactivated the absorbing capacity of fibroblasts for both antisera. Trypsin treatment of fibrosarcoma cells, which when untreated completely absorbed the anti-embryo serum, decreased their absorbing capacity. Additionally, normal untreated fibroblasts in growing phase were found to absorb the anti-embryo serum.