Effects of Sensitization to Dinitrochlorobenzene (DNCB) on Clinical Pathology Parameters and Mitogen-Mediated Blastogenesis in Cynomolgus Monkeys (Macaca, fascicularis)

Abstract

Immunotoxicologic testing of drug candidates and environmental contaminants is of growing importance. Cutaneous delayed type hypersensitivity (DTH) is a convenient way of testing immune function in vivo. However, DTH testing must not interfere with interpretation of other relevant parameters. We have evaluated the effects of sensitization and challenge with dinitrochlorobenzene (DNCB) on clinical parameters routinely evaluated in toxicity testing and on lectin-mediated blastogenesis. Female cynomolgus monkeys were sensitized to DNCB with 4 daily applications of DNCB in acetone to the skin of the axilla. Fifteen days later, the monkeys were challenged for DTH by applying DNCB to the antecubital skin. Skin fold thickness was measured and the macroscopic appearance of the challenge site was scored 24 and 48 hr after challenge. All 5 monkeys were successfully sensitized to DNCB. There was a significant increase in the mean skin fold thickness (compared to pre-challenge thickness) of 2 mm at 24 hr and 1 mm at 48 hr ( p < 0.001). The clinical score of the challenge site was also increased. Histologic examination of the sensitization and challenge sites from a second group of monkeys exposed to DNCB in an identical manner showed the perivascular inflammatory cell infiltrate typical of DTH. Evaluation of hematologic parameters at days 7, 14, and 21 revealed no change in the erythron at any interval and a mild decrease in total WBC, neutrophil and lymphocyte counts on day 7 in 4/5 monkeys. The WBC parameters remained within the normal range and returned to pre-sensitization values at the later intervals. Clinical biochemical parameters related to liver and kidney function were evaluated at the same intervals and no changes were found. The blastogenic response of peripheral blood leukocytes to concanavalin A, phytohemagglutinin and pokeweed mitogen was mildly but not significantly decreased at day 7 but not on day 14 or 21. This study has shown that sensitization to DNCB in cynomolgus monkeys is a reliable means of evoking a DTH response which is quantifiable. It has also shown that sensitization and challenge with DNCB can be incorporated into toxicity studies without confounding interpretation of other toxicity data.