In previous studies we observed that exposure of mice to the contact allergen 2,4-dinitrochlorobenzene (DNCB) and the respiratory allergen trimellitic anhydride (TMA) resulted in qualitatively different immune responses characteristic of selective Th1 - and Th2-type T helper cell activation respectively. The purpose of the present investigation was to determine whether the effects recorded with DNCB and TMA are characteristic of immune responses to contact and respiratory chemical allergens in general. Experiments have been performed with phthalic anhydride, a known human respiratory sensitizer, and with oxazolone, a potent contact allergen. Under conditions of exposure where both chemicals elicited an IgG anti-hapten antibody response, only phthalic anhydride caused an increase in the serum concentration of IgE. Furthermore, like TMA, phthalic anhydride preferentially induced IgG2b rather than IgG2a antibody. In contrast, oxazolone, like DNCB, induced a markedly stronger IgG2a than IgG2b antibody response.
These data provide confirmatory evidence that chemical respiratory allergens and chemical contact allergens elicit qualitatively different immune responses which reflect their clinical effects in man.