In Situ Immune Response Evaluation via Immunohistochemistry in Skin Biopsies from Patients Affected by Autoimmune Blistering Diseases

Introduction: The in situ immune response in skin biopsies from patients affected by autoimmune skin blistering diseases (ABD) is not well characterized. Aim: Our investigation attempts to immunophenotype cells in lesional skin in several ABD, utilizing immunohistochemistry (ICH). Methods: We tested by IHC for CD4, CD8, CD19, CD20, CD45, CD56/NCAM, PAX-5, granzyme B, myeloperoxidase, neutrophil elastase, LAT and ZAP-70 in patients affected by ABD. We tested 30 patients with endemic pemphigus foliaceus (EPF), 15 controls from the EPF endemic area, and 15 biopsies from healthy controls from the USA. We also tested archival biopsies from patients with selected ABD, including 30 patients with bullous pemphigoid, 20 with pemphigus vulgaris, 8 with pemphigus foliaceus and 14 with dermatitis herpetiformis. Results: We found a predominantly CD8 positive/CD45 positive T cell infiltrate in all ABD. Our skin biopsies demonstrated consistently positive staining for myeloperoxidase, but negative staining for neutrophil elastase. Most ABD biopsies displayed negative staining for CD4 and B cell markers; natural killer cell markers were also rarely seen. ZAP-70 and LAT were frequently detected. In El Bagre-EPF, a significant fragmentation of T cells in lesional skin was noted, as well as autoreactivity to lymph nodes. Conclusions: The documented T cell and myeloperoxidase staining are indicative of the role of T lymphocytes and neutrophils in lesional biopsies in patients with ABD, in addition to previously documented deposition of B cells, immunoglobulins and complement in situ. In El Bagre-EPF, T cells could also target lymph nodes; however, further studies are needed to confirm this possibility.