DEMONSTRATION OF THE COMPLEMENT REGULATING PROTEIN, BETA-1H, IN SKIN BIOPSIES FROM PATIENTS WITH BULLOUS PEMPHIGOID

.beta.1H-globulin is a recently characterized plasma protein which regulates the biologic activities of the major fragment of the 3rd complement component, C3b. The major function of this protein is to act as a cofactor for C3b inactivator (C3bINA) in the cleavage of C3b to an intermediate molecule, C3b'', consisting of an intact .beta.-chain covalently bound by disulfide bridges to 2 .alpha.-chain fragments of 40,000 and 67,000 daltons. Final cleavage of C3b'' to the C3c and C3d fragments requires an additional protease such as plasmin or elastase. Additionally, .beta.1H interferes with the activity of the alternative pathway convertases, .**GRAPHIC**. and .**GRAPHIC**. by displacing or competing with the binding of factor B. In this study, perilesional skin biopsies from 10 patients with active bullous pemphigoid were examined for the presence of .beta.1H at the dermal-epidermal junction by immunofluorescent methods. The protein was found in 8 of 9 biopsies in which C3 also was deposited. In a single case where C3 was not found, .beta.1H was not seen. .beta.1H apparently plays a role in the in vivo control of C3b and additional evidence was provided for the participation of the complement system in the pathogenesis of bullous pemphigoid.