Indirect immunofluorescence for the detection of autoimmune urticaria

Background: An autoimmune basis is believed to be responsible for about half of chronic spontaneous urticaria (CSU) cases. The autologous serum skin test is used as a possible indicator, but there is currently no test that directly indicates an autoimmune etiology. In this study, an indirect immunofluorescence was used to identify patients with autoantibodies directed at mast cells. Methods: Two substrates were used including paraffin embedded sections of skin biopsies from an infant with bullous mastocytosis and cord blood-derived mast cells (CBMC). Sera from 76 patients with CSU were incubated with substrates and conjugated with human IgG. Results: Using the bullous mastocytosis preparations, positive indirect immunofluorescence was found in 46% (n = 76), while the CBMC substrate was positive in 39% (n = 70). Conclusion: The IgG autoantibodies directed at mast cells could be detected in about half the patients with CSU. Indirect immunofluorescence should be considered as an indicator of the autoimmune form of CSU.