Epidermal Antibodies, Bullous Pemphigoid
Several blistering skin diseases are associated with specific autoantibodies. Pemphigus, a rare, but serious autoimmune skin disease is associated with serum antibodies directed against the cell surface of epidermal keratinocytes in 90% of patients. Pemphigus vulgaris is characterised by a unique autoantibody specific for an epidermal cell surface desmosomal antigen found on differentiating squamous cells. These antibodies are also detected in situ in biopsies from affected individuals.
Pemphigoid is an autoimmune skin disease that occurs in the elderly with 70- 90% patients having serum antibodies directed against the cutaneous basement membrane.
Other less common skin autoantibodies can be detected with these assays. The antigens associated with bullous pemphigus are found in the inter-cellular substance between the squames. They recognise desmoglein 1, a 160kDa glycoprotein recognised by antibodies in pemphigus vulgaris or the closely related, desmoglein 3, a 130kDa autoantigen of pemphigus foliaceus. Bullous pemphigoid is associated with autoantibodies recognising hemidesmosomal components of the epidermal basement membrane.
The antigens are mainly, a 220-240 kD protein (BPAG1) found in the intracellular domain of the hemidesmosome and a 165-180kD protein (BPAG2) found along the plasma membrane of the hemidesmosome. All of the commonly recognised skin antigens are also found in the squamous epithelium of the oesophagus.
Blistering skin diseases (pemphigus, pemphigoid).
70-90% of patients with pemphigus vulgaris have circulating autoantibodies. Levels correlate with disease activity.70-80% of patients with bullous pemphigoid have circulating antibodies but the levels do not correlate with disease activity. BPAG1 is recognised in 51%, BPAG2 in 49%. Antibody levels do not correlate with disease activity. Results can be confirmed by detection of deposited immunoglobulins and complement in skin biopsies by staining of tissue with fluorescently labelled rabbit anti-human antibodies recognising IgG, IgM, IgA or C3.
These autoantibodies are detected by indirect immunofluorescence using sections of monkey oesophagus.
Assay range notes
Pattern of staining given together with titre 1:10-1:320.