LN-3: a diagnostic adjunct in cutaneous graft-versus-host disease.

Expression of HLA Class II antigen on keratinocytes has been advocated as a diagnostic marker of acute graft-versus-host disease (GVHD). LN-3 is a murine monoclonal antibody marking an HLA Class II antigen that survives formalin fixation and paraffin embedding. We analyzed the LN-3 staining pattern on 56 skin biopsies from patients treated with bone marrow or peripheral stem cell transplantation, non-transplant patients receiving conventional chemotherapy and/or radiation therapy and controls. Keratinocyte staining, endothelial staining, and the number of epidermal and dermal Langerhans cells were evaluated and analyzed with respect to the histologic and clinical diagnosis in a blind and retrospective fashion. The most predictive parameter for GVHD was marking of endothelial cells by LN-3 which was present in 12 of 16 (75%) biopsies from patients with GVHD. Endothelial staining was found in a total of 19 biopsies of which 12 (63%) had GVHD. These data suggest that LN-3 immunohistochemistry may help identify cutaneous GVHD and discriminate it from conditions that are histologically similar.