Immunosuppressive effects of cyclophosphamide, vincristine, and L-asparaginase in dogs.

The acute effects of cyclophosphamide, vincristine, and L-asparaginase on the humoral and cell-mediated immune responses in dogs were evaluated. Dogs were given a single dose of cyclophosphamide (10 mg/kg of body weight, IV), a single dose of vincristine (0.025 mg/kg, IV), a single dose of L-asparaginase (400 U/kg, IV), or a combination of these drugs at the aforementioned dosages administered simultaneously. The total number of leukocytes decreased significantly (P = less than 0.05) on posttreatment day 3 in the cyclophosphamide-treated dogs. Antibody responses and lymphocyte blastogenesis were not affected. A transient lymphopenia on posttreatment day 1 was the only response seen in the vincristine-treated dogs. Antibody responses to sheep RBC and lymphocyte blastogenesis were suppressed in the L-asparaginase-treated dogs. L-Asparaginase did not affect the antibody response to bovine serum albumin or peripheral blood leukocyte counts. Suppressed antibody responses to sheep RBC and to bovine serum albumin, depressed lymphocyte blastogenesis, and decreased numbers of all peripheral blood leukocytes were seen in dogs given the 3 drugs in combination.