Contrasting effects of cyclophosphamide and prednisolone on the phenotype of human peripheral blood leukocytes.

The cell surface phenotype of human peripheral blood mononuclear cells has been characterized before and after intravenous injection of cyclophosphamide or prednisolone. Low doses of cyclophosphamide (100-600 mg/m2) temporarily decrease levels of circulating B lymphocytes. Slightly higher doses of cyclophosphamide (200-600 mg/m2) produce transient depression of T8-, M1-, and Ia-positive cells. After doses of 200-400 mg cyclophosphamide/m2, T4-positive cells are spared, resulting in a transient elevation of the T4/T8 ratio. With higher doses of cyclophosphamide (greater than or equal to 600 mg/m2), all T cells are affected and the T4/T8 ratio declines to pretreatment levels. By contrast, intravenous injection of prednisolone at 40 mg/m2 reduces the T4/T8 ratio. Levels of both T4 and T8 cells decline, but T4 cells are affected more markedly than T8 cells.