THE LOCALIZATION OF THE TARGET ANTIGENS AND ANTIBODIES IN LINEAR IGA DISEASE IS HETEROGENEOUS, AND DEPENDENT ON THE METHODS USED

Fifty-nine patients with linear IgA disease, 24 with onset in childhoo d and 35 with adult onset, were studied. Sera from all patients were t ested by indirect immunofluorescence, using as substrates intact norma l skin and normal skin which had been split through the lamina lucida region of the basement membrane zone by suction and by prolonged incub ation with molar NaCl. This enabled the site of the target antigen for the circulating IgA antibodies to be determined. The sites of deposit ion of the IgA antibodies in vivo were detected by raising a suction b lister in eight patients, and splitting seven patients' biopsies by pr olonged incubation with molar NaCl. Eighteen sera were positive with i ntact skin, and 34 with split skin. Twenty-nine sera were positive wit h suction blisters as substrate; 14 bound to the epidermal aspect of t he split skin, seven in a combined pattern (binding to the epidermis a nd dermis) and six to the dermal aspect. Thirty-one sera bound to salt -split skin, 24 to the epidermal side and seven on the dermal side. Th ere was discordance between the two methods of skin splitting in 15 se ra. Seven sera gave a combined pattern with suction but with salt-spli t skin, five of these bound epidermally, one was dermal, and one negat ive. Five sera showed epidermal binding on salt-split skin and were ne gative on suction blisters, and the reverse was seen with one serum. T wo sera gave variable results on suction blisters. Direct immunofluore scence studies showed dermal binding on all eight patients with suctio n blisters, and epidermal binding in four and dermal binding in three patients with salt splitting. These results demonstrate that the locat ion of the target antigens and the sites of deposition of the antibodi es are dependent on the methods used. They also suggest that there are at least two different antigens, an epidermal- and a dermal-associate d antigen. The sera reacting in the combined pattern may represent ant ibodies reacting with a different epitope of the epidermal antigen, wi th a further epidermal antigen, or with two target antigens.