Cell populations in experimental contact dermatitis.

Sequential biopsy specimens from contact dermatitis induced in the guinea pig by the application of dinitrochlorobenzene were studied by histologic, histochemical, and electron microscopical methods. At 12 hours, mononuclear cells and polymorphonuclear cells reached their peak numbers. Increasing numbers of basophils were observed, and at 24 and 48 hours, the basophils reached their maximal numbers. The basophils were observed not only in the dermis but also in the epidermis, and they may have had an active role in inflammation or repair. A close relationship was noted between the macrophage and all of the successive cell populations in the dermis.