Elevated serum osteopontin levels in patients with severe cutaneous adverse drug reactions.

Osteopontin (OPN) was initially described as a protein involved in bone metabolism, but the roles played by OPN in the immune system and allergic reactions have attracted increasing attention. Here, we clarify the OPN-related dynamics of severe cutaneous adverse drug reactions, and assess whether the OPN level has utility for classifying such reactions and serving as a biomarker of severity. Serum OPN levels in patients with drug-induced hypersensitivity syndrome/drug reaction with eosinophilia and systemic symptoms (DIHS/DRESS), Stevens-Johnson syndrome/toxic epidermal necrolysis (SJS/TEN) and erythema multiforme-type drug reaction (EM-DR) were quantified by ELISA. The OPN sources were analyzed by dual immunofluorescence assay of DIHS, SJS/TEN and EM-DR biopsy specimens. The serum OPN levels of DIHS/DRESS patients (489.1 ± 37.0 ng/mL) and SJS/TEN patients (508.5 ± 47.8 ng/mL) were significantly higher compared with controls (314.4 ± 14.3 ng/mL; p < 0.001). After treatment, the serum OPN level of DIHS/DRESS patients decreased to that of controls. In addition, OPN levels in DIHS/DRESS patients and SJS/TEN patients were higher than in patients with EM-DR (Mann-Whitney U test, p < 0.05). However, when the Kruskal-Wallis test was used to compare the OPN levels among the three groups of patients, the difference was not significant (p = 0.055). Dual immunofluorescence assay revealed that T lymphocytes and macrophages were the main OPN sources in DIHS, SJS/TEN and EM-DR patients. These data suggest that the OPN level can be used to evaluate the severity of inflammation in patients experiencing drug reactions.

Reduced expression of programmed cell death 1 and programmed cell death ligand 1 in infiltrating inflammatory cells of lichen planus without administration of immune checkpoint inhibitors.

Keratinocytes are the main targets of infiltrating T cells in the pathogenesis of lichen planus. However, the mechanisms of dense inflammatory infiltrates beneath the epidermis remain unknown. The aim of the present study was to clarify the roles of programmed cell death 1 (PD-1) and its ligand (PD-L1) in the pathogenesis of lichen planus. Immunohistochemistry of PD-1 and PD-L1 in 12 cases each of lichen planus and dermal-type erythema multiforme was performed. The expression of PD-1 and PD-L1 on infiltrating inflammatory cells, predominantly lymphocytes in lichen planus, was significantly less compared to that in dermal-type erythema multiforme. By dual immunofluorescence, the overlap between PD-1 and leukocyte common antigen, CD4, CD8, CD68, and factor XIIIa was limited and found in only a very small portion of lichen planus cells. Our data suggest that decreased expression of PD-1 and PD-L1 could play a role in accelerating inflammatory cell infiltration targeting the epidermis in the pathogenesis of lichen planus.