6 zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFED The Pe m p hig us A ntig e ns zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQ Ra mzy S. La b ib , M.D., Ph.D., Ha rish Pa te l, M-D,, G ra nt J. Anha lt, M.D., a nd Luis A. Dia z, M.D. zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA From the Department of Dermatology, The Johns Hopkins University School of Medicine, Baltimore, Maryland Supported by U.S. Public Health Service grants (ROl-AM-32081-01. R23-AM-32079 and R23-AM-32490-01) from the National Institutes of Health and a gift from the Estee Lauder Corpo- ration. Dr. H. Pate1 is a recipient of an Avon Fellowship from the Dermatology Foundation. Pemphigus antigens are normal squamous epithelial tissue con- stituents that are identified by their reaction with autoantibodies found in the serum of patients with active pemphigus vulgaris or any of the other types of pemphigus (i.e., vegetans, erythematosus, and foliaceous). The characteristic lesion of pemphigus is epider- ma1 suprabasilar cell-cell detachment (acantholysis). It is impor- tant to note that pemphigus antigens are present in the intercellular substance (ICS) of stratified squamous epithelia where this process of acantholysis occurs. There is increasing evidence that pemphi- gus antigens are heterogenous, but whether this heterogeneity is due to the existence of different antigen molecules or different antigenic determinants on the same molecule is not yet clear. The use of the word antigens in this article does not imply commitment or rejection of any of these alternative explanations. Me tho d s o f De te c tio n a nd Q ua ntita tive De te rm ina tio n Immunofluorescence Technique Indirect immunofluorescence (IF) was the first method used to detect and define pemphigus antigen.’ Earlier investigations using complement fixation,2j3 agglutination of collodion particles,4 or red blood cells5 coated with extracts of normal human skin or pemphi- gus blister fluid could detect antibodies in the serum of pemphigus patients, but the specificity of this reaction was doubtful. These methods, in contrast to IF techniques, could not define the histolog- ical distribution of the antigen, and some of them2y3 could not be reproduced by other investigators.677 Although indirect IF is an excellent procedure for studying the histologic distribution of the antigens, it is largely subjective, difficult to standardize, and is qualitative rather than quantitative. Blocking of the indirect IF staining produced by pemphigus serum on squamous epithelial ICS by preincubation of pemphigus serum with preparations contain- ing pemphigus antigen can be used as a semiquantitative method for determination of the antigen concentration in these prepara- tions.* It is also possible to perform blocking of the direct IF staining zyxwvutsrqpo a2