Pemphigus and pemphigoid antigens are expressed in human amnion epithelium

The sera of patients with pemphigus vulgaris (PV) and bullous pemphigoid (BP) contain autoantibodies which react with antigens present in a variety of mammalian squamous epithelia. The biologic role of these epithelial antigens is unknown; however, they do appear to be markers of epithelial differentiation. We have examined many human tissues that may be used as sources of large amounts of BP and PV antigens, including the human amnion, which is composed of the amnion reflectum and placentum (epithelial monolayers) and amnion cord (stratified epithelium). Human amnion was obtained from normal term deliveries and specimens of each area of the amnion were processed for light and electron microscopy. Samples of amnion were snap-frozen in liquid nitrogen and 4-micron sections were used as a substrate for BP and PV antibodies by indirect immunofluorescence (IF) techniques. Well-characterized BP serum (indirect IF titer 1:2560), PV serum (indirect IF titer 1:160), and normal human serum (negative indirect IF) were utilized as sources of BP and PV autoantibodies and a negative control, respectively. Linear staining of the BMZ was produced by BP antibodies in 8/8 specimens of amnion reflectum, 8/8 specimens of amnion placentum, and 3/3 specimens of amnion cord. Staining of the epithelial intercellular spaces was produced by PV antibodies of 2/3 specimens of amnion cord and none of the amnion reflectum (0/8) or amnion placentum (0/8) tested. Normal human serum produced no specific staining of the amnion. The light and the ultrastructural features of human amnion basement membrane zone and intercellular spaces resembles closely their epidermal counterparts. The restricted distribution of BP antigen in amnion epithelial basal cells (amnion reflectum, placentum, and cord) and PV antigen in stratified amnion epithelium (amnion cord) reinforces their relationship with epithelial differentiation. The abundance and availability of these tissues facilitate extraction and characterization of BP and PV antigens.