Influence of topical exposure to chemical allergens on murine langerhans cells. Comparison of 2,4-dinitrochlorobenzene with trimellitic anhydride

Chemical allergens differ with respect to the type of hypersensitivity reactions they preferentially elicit. Some chemicals, such as trimellitic anhydride (TMA), have the potential to induce both contact and respiratory hypersensitivity. Other chemicals cause only contact allergy. For example, 2,4-dinitrochlorobenzene (DNCB), a potent contact allergen, appears not to induce respiratory sensitization. In previous studies we have shown that topical exposure of mice to TMA and DNCB, under conditions of equivalent immunogenicity with respect to draining lymph node activation and contact sensitization. caused qualitatively different antibody responses. While the chemicals provoked IgG anti-hapten antibody responses of equivalent magnitude, only TMA induced an IgE response, and DNCB caused a significantly stronger IgG2a response. These data are consistent with the preferential activation by DNCB and TMA of Th1 and Th2 cells respectively. The purpose of the present study was to examine whether the qualitative differences in immune responses stimulated by these chemicals is reflected by variable affects on Langerhans cells (LC) in situ. Mice were exposed to concentrations of DNCB (1%) and TMA (50%) which caused equivalent levels of contact sensitization. Under these conditions topical exposure to DNCB, but not to TMA, or to vehicle alone, resulted in increased expression by LC of Ia antigen. Similar treatment with an irritant concentration (20%) of sodium dodecyl sulphate failed to influence Ia expression by LC. These data indicate that, at concentrations which induce similar levels of skin sensitization, not all contact allergens cause rapid changes in LC Ia expression, and that the qualitative differences in immune responses elicited by chemical allergens DNCB and TMA is associated with variable effects on LC.