Paraneoplastic pemphigus (PNP) is a recently described autoimmune mucocutaneous disease occurring in combination with neoplasia. Serum from patients immunoprecipitates a characteristic complex of four epidermal antigens (Ag) with molecular
weights
of
250, 230, 210 and 190-kD. The objective of this study is to characterize the PNP Ag by immunoblotting and immunoelectron microscopic(IEM) examination. We investigated the Ag molecules by immunoblot analvsis in six patients with PNP. All the PNP
sera
reacted with the 210-kD and the 190-kD proteins. However, 250-kD desmoplakin 1 Ag were detected in only 2 patients sera, and the 230-kD bullous pemphigoid Ag was not detected in any patients sera. We further characterized the 210-kD and 190-kD Ag
which
are considered major PNP Ag by immunoblot analysis using affinity-purified antibodies against these Ag .Autoantibodes specific for each of the 210-kD and 190-kD Ag were prepared by immunoaffinity against antigens immobilized on nitrocellulose and
released by acid glycine. An IgG specific for the 210-kD Ag and another IgG specific for the 190-kD ag were reacted with both the 210-kD and the 190-kD Ag, and the 210-kD Ag band was much more intense than the 190-kD Ag band. Direct IEM
examination
was
performed on sections of fresh-frozen skin of a PNP patient whose serum contain antibidies against the 210-kD and 190-kD Ag. The IgG deposits were located within the intercellular spaces between keratinocytes, both in desmosomal and nondesmosomal
areas
This immunoblot analysis shows that PNP sera show two patterns of immune reactivity i. e., majority of PNP sera react with the 210-kD and 190-kD Ag besides the 210-kD and 190-kD ag. This study suggest that the 210-kD and the 190-kD proteins are
major
PNP Ag which are localized to the intecellular spaces between keratinocytes. And the 190-kD protein may be a degradation product or a modified protein of 210-kD Ag.
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