Skin reactivity in guinea pigs sensitized with 2,4-toluene diisocyanate

Skin reactivity in guinea pigs sensitized with 2,4-toluene diisocyanate (TDI) has been examined. For sensitization, guinea pigs were treated daily with a 10% TDI solution in ethyl acetate by intranasal application for 5 consecutive days. Local application of TDI onto the flank skin of these TDI-sensitized animals resulted in an immediate development of the flare-and-wheal reaction at the site of application. The extent of the skin response was dependent on the concentration of TDI used for provocation. It was also demonstrated that the skin reactivity was successfully transferred to untreated animals by injecting sera obtained from actively sensitized animals. However, heat treatment of sensitized sera resulted in a slight, but not significant decrease in its ability to sensitize recipient animals. Histological examination revealed degranulation of mast cells and infiltration of basophils and eosinophils in the superficial dermis as the characteristics of the skin reaction in the immediate and late phase, respectively. Pretreatment of TDI-sensitized animals with dexamethasone, a steroidal agent, mepyramine, an antagonist of the histamine H1 receptor, or several antiallergic agents including ketotifen, azelastine and oxatomide resulted in a significant inhibition of the skin reactivity. However, some antiallergic agents such as tranilast, ibuzilast and DSCG were not effective in inhibiting this skin reactivity.