LONG-LASTING ALLERGIC PATCH TEST REACTIONS TO NICKEL SULFATE - ANALYSIS BY NICKEL QUANTIFICATION AND IMMUNOCYTOCHEMISTRY

We previously showed the median duration of positive patch test reacti ons to nickel sulfate (5% pet.) was 9 days, and defined as long-lastin g (LLAPTR) the 14.3% of reactions that persisted for 17 days or longer . The pathomechanisms of LLAPTR are unclear, but may involve either lo calized antigen persistence or abnormal downregulation of the cellular immune response. In this study, we compared (a) the nickel concentrat ion and (b) the immunocytochemical nature of the local immune reaction , between biopsies from LLAPTR (n=8) and normally resolving allergic p atch test reactions (NRAPTR) (n=8) to nickel sulfate. The concentratio n of nickel in LLAPTR (median 0.56 mu g/g, range 0.25-3.87 mu g/g, mea n 0.83 mu g/g, 95% CI 0.35-1.31) and NRAPTR (median 0.58 mu g/g, 0.2-1 .85 mu g/g, mean 0.88 mu g/g, 95% CI 0.02-1.74) was similar. Activated T lymphocytes, expressing surface IL-2 receptor, HLA DR, DR alpha 1, DP, DQ, and CD2>CD8>CD4 antigens, were seen throughout the dermis and occasionally infiltrating the suprabasal layer of the epidermis in all biopsies. CD1 and HLA DR, DR alpha 1, DP, and DQ-expressing Langerhan s cells were present throughout the epidermis and occasionally seen in the papillary dermis. HLA DR, DR alpha 1, DP, and DQ antigen expressi on were also seen on the surface of non-dendritic cells in the epiderm is (probably either keratinocytes or T lymphocytes) and vascular endot helial cells in the papillary dermis. There were no significant qualit ative or quantitative differences in the immuno-cytochemical nature of the localized immune reaction between LLAPTR and NRAPTR. These findin gs suggest that the pathomechanism of LLAPTR to nickel sulfate is unli kely to be explained simply on the basis of nickel concentration or th e nature of the localized immune reaction at the patch test site. (C) Munksgaard, 1996.