Immunotoxic effects of cyclophosphamide and cyclosporine in the dog

Limited non-clinical immunotoxicity data are available in the dog, although this is a major non-rodent species in regulatory safety studies. The present study aimed to test whether widely accepted immunotoxicity endpoints including lymphocyte subset immunophenotyping, the anti-KLH TDAR assay, and histological examination of the main lymphoid organs were reliable to detect immunosuppression induced by cyclosporine and cyclophosphamide in dogs and could, therefore, be used for non-clinical immunotoxicity evaluation in this species. Male and female Beagle dogs were treated orally from Day 1 for 4 weeks with 25 mg/kg cyclosporine daily, or with 2 mg/kg cyclophosphamide on 4 consecutive days each week, or the same volume of drinking water daily. Blood samples were withdrawn pre-test and on Days 11, 18, and 23 to measure standard hematology parameters and analyze lymphocyte subsets. All animals received an intramuscular injection of 5 mg KLH on Day 11. Sandwich ELISA assays were used to quantify anti-KLH IgM an...