Toluene diisocyanate (TDI) disposition and co-localization of immune cells in hair follicles.

Diisocyanates (dNCOs) are potent chemical allergens utilized in various industries. It has been proposed that skin exposure to dNCOs produces immune sensitization leading to work-related asthma and allergic disease. We examined dNCOs sensitization by using a dermal murine model of toluene diisocyanate (TDI) exposure to characterize the disposition of TDI in the skin, identify the predominant haptenated proteins, and discern the associated antigen uptake by dendritic cells. Ears of BALB/c mice were dosed once with TDI (0.1% or 4% v/v acetone). Ears and draining lymph nodes (DLNs) were excised at selected time points between 1 h and 15 days post-exposure and were processed for histological, immunohistochemical, and proteomic analyses. Monoclonal antibodies specific for TDI-haptenated protein (TDI-hp) and antibodies to various cell markers were utilized with confocal microscopy to determine co-localization patterns. Histopathological changes were observed following exposure in ear tissue of mice dosed with 4% TDI/acetone. Immunohistochemical staining demonstrated TDI-hp localization in the stratum corneum, hair follicles, and sebaceous glands. TDI-hp were co-localized with CD11b(+) (integrin αM/Mac-1), CD207(+) (langerin), and CD103(+) (integrin αE) cells in the hair follicles and in sebaceous glands. TDI-hp were also identified in the DLN 1 h post-exposure. Cytoskeletal and cuticular keratins along with mouse serum albumin were identified as major haptenated species in the skin. The results of this study demonstrate that the stratum corneum, hair follicles, and associated sebaceous glands in mice are dendritic cell accessible reservoirs for TDI-hp and thus identify a mechanism for immune recognition following epicutaneous exposure to TDI.