Immunological responses of weanling cotton rats (Sigmodon hispidus) to acute benzene and cyclophosphamide exposure

The immunological effects of benzene and cyclophosphamide (CY) on 21-d-old weanling cotton rats were investigated. The rats were exposed to 100 or 1000 mg/kg of benzene and to 50 mg/kg CY. In rats exposed to CY and benzene, relative weights of thymus glands were significantly depressed compared to controls, while liver and kidney weights were increased only in rats exposed to CY. Exposure to CY resulted in white blood counts, hematocrits, and viable spenocyte yields being significantly depressed compared to benzene and controls. Exposure to CY also resulted in a significant depression in delayed-type hypersensitivity responsiveness compared to those exposed to benzene and controls. Overall, the data indicated that acute benzene exposure did not induce suppression or stimulation of the immune system, which contradicts earlier study results. Possible reasons for this discrepancy are discussed.