Common antigen expression between human periderm and other tissues identified by GB1-monoclonal antibody

From 4 weeks estimated gestational age (EGA) until the end of the second trimester (24 weeks EGA) the fetal epidermis is covered by a specialised epithelium, the periderm. The origin and function of periderm remain speculative. We have demonstrated, using indirect immunofluorescence and immunoperoxidase staining, that periderm is recognised by a mouse IgM monoclonal antibody (Mab) GB1, which has been raised against a simple extract of human amnion. Immunoelectron microscopy localises GB1 to the amniotic surface of periderm, particularly in association with the microvilli, and also bordering cellular identations of the periderm cells. GB1 antigen (ag) is also expressed by the epithelium of fetal oesophagus, fetal and adult conjunctiva and cornea but is absent in a variety of other fetal and adult tissues including bladder, oral mucosa and thymus. The similar distribution of GB1 ag in both periderm and membranes possibly suggests a common origin and the shared expression with fetal oesophagus and fetal and adult eye may indicate a function related to the fluid environment. We therefore feel that GB1 Mab may be of use in further investigations into the origin, structure and function of human periderm.