Immunologic relatedness of intracisternal A-particles in mouse embryos and neoplastic cell lines.

Murine intracisternal A-particles (IAP) are retroviruses expressed in large numbers in certain neoplastic cells and preimplantation mouse embryos. Immuno-electron microscopic detection of IAP-associated antigens in mouse rhabdomyosarcoma cells and early mouse embryos provides the first direct evidence that IAP produced by these two sources are serologically related. In both embryos and cells, data suggest that, after synthesis, IAP core protein rapidly associates with the endoplasmic reticulum. In addition, in embryos only, data confirm earlier observations that IAP-associated antigens are expressed on the cell surface. There is no evidence that the Golgi apparatus is involved in the processing of IAP antigens in either cell type.