Low-dose cyclophosphamide enhances helper-to-non-helper ratios

This study was conducted to analyze the effect of different doses of cyclophosphamide (CY) on the lymphocyte populations in the rat. Monoclonal antibodies against rat determinants were used: W3/13 (T lymphocytes), W3/25 (T helper), OX-8 (non-helper), and OX-33 (B lymphocytes). Blood samples were collected on days 0, 3, 7, and 14 from four groups of F-344 Fisher rats (n = 4): three that received 25, 50, or 75 mg/kg of CY and a control group. The duration and severity of lymphocyte depletion were dose-related and were evident for both helper and non-helper cells (p less than 0.02). The helper-to-non-helper ratio increased for the group that received 25 mg/kg when compared with control and other groups, but was only significantly changed when compared with the 75 mg/kg group (p = 0.004). This effect was transitory and was only seen on day 3. The control and the 25 mg/kg groups gained weight; the other two groups lost weight (p less than 0.05). Lower doses of CY were associated with a transitory immunostimulatory effect and no morbidity when compared with higher doses.