Immunosuppressive effect of cyclophosphamide on white blood cells and lymphocyte subpopulations from peripheral blood of Balb/c mice

There has been lack of the uniform standard for establishment of animal immunodepressive models induced by cyclophosphamide (CTX), and the information about the immunosuppressive effect of CTX on peripheral blood lymphocyte subsets in rodents. Here we describe a CTX-induced mouse model and try to establish a feasible immunosuppressive model for studying the fungal pathogenicity. Balb/c mice received two intraperitoneal injections of different CTX doses (50-200 mg/kg) at 2-day intervals. Peripheral whole blood collected at different time-points before and after CTX injection was used to detect white blood cells (WBCs), lymphocytes and their subsets by automated hematology analyzer and flow cytometry, respectively. WBCs and lymphocytes in all groups except CTX50 (50 mg/kg CTX) group commenced to decrease in a dose-dependent manner on day 1, reached the nadir on day 4, rebounded on day 10, and declined again on day 17 after CTX treatment. Low dose (50 mg/kg) CTX produced no obvious change of percentage of CD3(+), CD4(+) and CD8(+) T cells and CD19(+) cells, but high doses (100 or 150 mg/kg) yielded a significant decrease of CD3(+) and CD4(+) cells on day 4 and CD19(+) cells on day 10, and increase of CD8(+) cells on day 4. The CD4(+)/CD8(+) ratio decreased on day 4, followed by a rebound thereafter when treated with 3 different doses of CTX. The results indicate that two intraperitoneal injections of CTX at 150 mg/kg at 2-day intervals may establish good immunosuppressive models of Balb/c mice for studying the fungal pathogenicity.