Immunoglobulin light and heavy chain isotypes in skin diseases: Restricted distribution in bullous pemphigoid and linear IgA bullous dermatosis

To assess the heterogeneity of immunoglobulins involved in various skin diseases, direct and indirect immunofluorescence studies of skin biopsies and sera, respectively, for κ and λ light chains, were performed. The anti-basement membrane zone (anti-BMZ) antibodies of patients with bullous pemphigoid showed a predominance of κ light chains, and patients with linear IgA bullous dermatosis showed a predominance of one light chain that was sometimes κ and sometimes λ. The bullous pemphigoid autoantibodies were then studied for IgG subclass distribution; a predominance of IgG4 was found. Although other explanations are possible, the light chain restriction in bullous pemphigoid most likely reflects heavy chain restriction and preferential association of heavy and light chain isotypes. The basis of the heavy chain restriction is not apparent. The light chain restriction in linear IgA bullous dermatosis may represent a restricted idiotypic repertoire.