4-chloro-o-phenylenediamine (CPD) was selected for evaluation as a sensitizing agent for contact hypersensitivity in mice. 4-chloro-o-phenylenediamine is used in dyes and is, therefore, a dyestuff intermediate. It is also used in the manufacture of 5-chlorobenzotriazole.
The objective of this study was to determine the sensitizing potential of 4-chloro-o-phenylenediamine when applied dermally to female B6C3F1 mice.
4-chloro-o-phenylenediamine was tested on female B6C3F1 mice. The doses of 4-chloro-o-phenylenediamine ranged from 1% to 10% in a solution of 4 parts acetone to one part olive oil (4:1) for sensitization and 10% for challenge. Mice received 20 µl by direct dermal application for 5 consecutive days to a prepared site. DNFB (1-fluoro-2,4-dinitrobenzene) (99.6%, Sigma Chemical Co.) was used as a positive control at a concentration of 0.5%. Measurement of allergic contact hypersensitivity was accomplished by a radioisotopic assay and the mouse ear swelling test.
A dose-dependent contact hypersensitivity response to 4-chloro-o-phenylenediamine was demonstrated in mice by the radioisotopic assay whether or not the site of sensitization was prepared using Freund's complete adjuvant. However, a statistically significant response was observed only in animals prepared using adjuvant and sensitized with 10% 4-chloro-o-phenylenediamine. The mouse ear swelling test detected a dose-dependent contact hypersensitivity response without adjuvant pretreatement at one and two days after challenge. A statistically significant response was detected only on the first day following challenge in mice sensitized and challenged with 10% 4-chloro-o-phenylenediamine.
The studies were conducted at the Medical College of Virginia Immunotoxicology Laboratory under NTP Contract No. ES 55094. The in-life phase of the studies was conducted between 1 October 1987 and 16 November 1987. The animals were housed in the animal facility of the Strauss Building. To the best of our knowledge, no significant deviations from Good Laboratory Practices occurred that affected the quality of the data and the ability to interpret the data with respect to the sensitizing potential of 4-chloro-o-phenylenediamine.