FACS analysis of the effects of MPA on cell cycle progression in stimulated human T lymphocytes: (A) Resting T lymphocytes; (B) T lymphocytes stimulated with IL-2/PHA-L for 48 hours; (C) T lymphocytes stimulated with IL-2/PHA-L and cocultured with 1 μmol/L of MPA; and (D) T lymphocytes stimulated with IL-2/PHA-L and cocultured with 1 μmol/L of MPA, 50 μmol/L of guanosine and 100 μmol/L of 8-aminoguanosine under conditions previously shown to increase guanine nucleotide pools.13 Cells were analyzed by FACS for DNA content and cell-cycle distribution, as outlined in the Materials and Methods section.