The differential sensitivity of rat peripheral blood T cells to immunosuppressants: cyclophosphamide and dexamethasone.

Peripheral blood T cells from rats given a single oral dose of dexamethasone (DMS) or cyclophosphamide (CY) exhibited a differential sensitivity to these compounds as measured by lymphoproliferation in the presence of concanavalin A (Con A) or phytohemagglutinin hemagglutinin (PHA). Con A-responsive cells (T Con A) were found to be resistant to the effects of DMS, while the PHA-responsive population (T PHA) showed a dose-dependent suppression at dose levels of 0.35 and 1.00 mg/kg. DMS did not alter serum antibody production against sheep erythrocytes at the dosage level which produced a significant depression of the PHA response. Animals treated with CY showed enhanced Con A-mediated lymphoproliferation at a dose of 15 mg/kg and marked suppression at 45 mg/kg. The PHA-mediated response, however, exhibited only a dose-dependent suppression at both dosage levels. CY had no effect on the antibody response at doses that enhance Con A lymphoproliferation. These results suggest that T helper cells and T suppressor cells are not TpHA cells.