A new synthetic compound, 6-hydroxy-2-tosylisoquinolin-1(2H)-one (2-OH), was selected for immunopharmacological activity tests. The effects of 2-OH on human peripheral blood mononuclear cell (PBMC) proliferation were determined by tritiated thymidine uptake. Compared to phytohemagglutinin (PHA; 5 microg/mL) stimulation, 2-OH significantly enhanced PBMC proliferation in a dose-dependent manner. The 50% enhancement activity (EC(50)) for 2-OH was 4.4+/-0.1 microM. In addition, effects of 2-OH on interleukin-2 (IL-2) and interferon-gamma (IFN-gamma) production in PBMC were determined by enzyme immunoassay. Results demonstrated that 2-OH stimulated IL-2 and IFN-gamma production in PBMC. Data from reverse transcription-polymerase chain reaction (RT-PCR) and real-time PCR indicated that IL-2 and IFN-gamma mRNA expression in PBMC could be induced by 2-OH. Therefore, 2-OH enhanced IL-2 and IFN-gamma production in PBMC by modulation their gene expression. We suggest that 2-OH may be an immunomodulatory agent.