Characterization of antibodies to antigens of the human amnion.

The specificities of antisera produced in nine rabbits to seven different preparations of human amniotic epithelium and controls were studied by immunofluorescence on cryostat sections of human amniochorions, placentae and a large collection of other tissues. Three different groups of reaction patterns were identified with the use of these antibodies, indicating the presence of at least three antigenic groupings which have been tentatively designated as amnion antigens 1 (AA1), amnion antigens 2 (AA2) and amnion antigens 3 (AA3). The AA1 group was found on the ectodermal tissues of breast ductal and corneal epithelium as well as on Hassall's corpuscles, while the AA2 group was also found on breast ductal and corneal epithelium and basal keratinocytes, but not on Hassall's corpuscles. The AA3 group was found on basement membranes of ectodermally derived epithelium, but was negative on kidney. The identification of the distribution of antigens in common with ectodermal tissues and extra-embryonic membranes suggests that human amnion and chorion may have a close embryological relationship with embryonic ectoderm and its subsequent products of organogenesis.