Localization of H blood group antigen in ectoblastic derivatives of murine teratocarcinoma

Ectoblastic derivatives (ectodermal and neuroectodermal components) constitute more than 90% of all structures in the murine teratocarcinoma derived from the PCC4-aza-1 line. This tumor was labeled immunocytochemically with fluoresceinated antibodies to A, B and H blood groups. A and B antigens were always noted to be absent from all structures of the three germ layers. With anti-H, however, embryonic and fetal endodermal components, e.g. alimentary or respiratory duct-like structures, gave positive staining. Mesodermal components, i.e. bone and cartilage structures, fibroblasts and myocytes of mature or embryonal type, were negative. Immature and mature ectodermal components, viz. epidermoid cysts or islets, were always positive. Neuroectodermal components, neuroblastic cysts and differentiated neuronal, glial and ependymal elements were always negative. Ectoblastic and/or neuroectoblastic individual cells or cell clusters, observed in the vicinity of positive differentiating ectodermal and neuroectodermal structures, were positive. Similar cells or clusters were negative when located close to negative neuroectodermal components. The undifferentiated, embryonal carcinoma cells and structures were always negative. These observations are compared to the staining patterns of H antigen in murine embryos and adult mice and in human teratocarcinomas. It is suggested that poorly differentiated, morphologically similar ectoblastic and/or neuroectoblastic structures are positive, if they concern ectodermal components, and negative, if they belong to neuroectodermal components, with the exception of some primary sensory cells that are positive. These last cells are also positive in normal fetal and adult tissues.