Human amnion membrane as a substrate for the detection of autoantibodies in pemphigus vulgaris and bullous pemphigoid.

BACKGROUND Human amnion membrane (HAM) was suggested to be a superior antigenic substrate for immunoblotting in detecting autoantibodies of autoimmune bullous skin diseases. OBJECTIVES To determine the properties of HAM as an antigenic substrate for the detection of autoantibodies in pemphigus vulgaris and bullous pemphigoid. METHODS Immunomapping and tandem liquid chromatography mass spectrometry were used to delineate the antigenic structure of HAM. Immunoblotting and indirect immunofluorescence were used to study the diagnostic utility of HAM in 25 pemphigus patients, 41 pemphigoid patients, and 36 controls, and the results were compared to those of indirect immunofluorescence on monkey esophagus, immunoblotting using normal human skin, and enzyme-linked immunosorbent assay. RESULTS Immunomapping demonstrated the presence of all the antigens known to be targeted in autoimmune bullous skin diseases, in both normal human skin and HAM, except for the absence of BP230, and low threshold levels of Dsg1, Dsg3 and Dsc3 in HAM. HAM indirect immunofluorescence demonstrated anti-basement membrane zone antibodies in 48.7% of the pemphigoid patients, and anti-intercellular space antibodies in 72.0% of the pemphigus patients. HAM immunoblotting did not demonstrate anti-BP230 antibodies, but detected anti-BP180 antibodies in 53.7% of the pemphigoid patients. It did not demonstrate anti-Dsg1 and/ or anti-Dsg3 antibodies in any of the pemphigus patients. These results were inferior to those of ELISA and monkey esophagus indirect immunofluorescence. CONCLUSIONS Compared to other studied methods, HAM does not offer advantages in detecting autoantibodies in bullous pemphigoid and pemphigus vulgaris.