In this study, the furofuran lignan (+)-diayangambin [tetrahydro-1,4-bis(3,4,5-trimethoxyphenyl)-(1 R)-1alpha,3abeta,4alpha,6abeta-1 H,3 H-furo [3,4- c]furan] was evaluated in vitro and in vivo for its immunomodulatory and anti-inflammatory efficacy. Human mononuclear cell proliferation was inhibited by diayangambin with an IC 50 value of 1.5 (0.5 - 2.8) microM. In addition, the compound reduced for 40.8 % prostaglandin E 2 generation in stimulated RAW 264.7 macrophage cell line at 10 microM. In vivo, a clear reduction of ear swelling was observed when diayangambin (40 mg/kg) was administered orally to 2,4-dinitrofluorobenzene-treated mice. The inhibition of swelling was associated with a reduction of leukocyte infiltration determined as myeloperoxidase activity. In the carrageenan mouse paw edema model, diayangambin significantly suppressed inflamed paw volume and prostaglandin E 2 levels. Our findings indicate the potential interest of diayangambin in the treatment of immune and inflammatory responses.