IgA1 is the major IgA subclass in cutaneous blood vessels in Henoch-Schonlein purpura

Henoch-Schonlein purpura (HSP) is characterized by palpable purpura predomi nantly involving the lower extremities. On direct immunofluorescence IgA ca n be seen deposited in the blood vessel walls of the superficial dermis. Th e subclass distribution of antibodies to this IgA was studied in the biopsi es of 28 patients with HSP by direct immunofluorescence using anti-IgA1 and anti-IgA2 specific monoclonal antibodies. All 28 patients' biopsies demons trated deposition of IgA1 while only one patient: had IgA2 deposition. Posi tive and negative controls stained appropriately. This demonstrates that Ig A1 is the dominant IgA subclass found in the skin in Henoch-Schonlein purpu ra.