Studies of autoantigens recognized by IgA anti-keratinocyte cell surface antibodies

We have examined autoantigens for IgA anti-keratinocyte cell surface antibodies in 17 intercellular IgA vesiculopustular dermatosis (IAVPD) cases showing only IgA antibodies and 5 cases showing both IgG and IgA antibodies (G/A cases). IAVPD cases were divided into two subtypes: (1) intraepidermal neutrophilic IgA dermatosis type showing pustule formation throughout the epidermis and IgA antibodies reactive with the entire epidermis and (2) subcorneal pustular dermatosis type containing IgA antibodies reactive with the uppermost portion of the epidermis. Most G/A cases showed atypical clinical features. With immunoblot analysis of normal human epidermal extracts, IgA antibodies in these cases showed no specific reactivity with either pemphigus foliaceus antigen (desmoglein 1) or pemphigus vulgaris antigen (desmoglein 3), except that IgG antibodies in one G/A case each recognized one of the two antigens. With immunoblotting of desmosome enriched fraction obtained from bovine snout epidermis, IgA antibodies in 10 IAVPD and 3 G/A cases and IgG antibodies in 4 G/A cases showed reactivity with either desmoglein 1 or desmocollin, another desmosomal cadherin. These results indicate that IAVPD and G/A cases are heterogeneous in terms of both clinical features and antigens and that the IgA autoantibodies in these cases may react with different antigens from those for IgG autoantibodies.