The anti-arthritic property of hydro alcoholic extract of Pterodon pubescens seeds was previously demonstrated using the Collagen Induced Arthritis (CIA) in mice, the most similar arthritis experimental model to human rheumatoid arthritis. This disease is characterized by chronic inflamed joints resulting from exacerbated functions of macrophages and T and B lymphocytes. Anti-inflammatory and antinociceptive activities by ethanolic extract of Pterodon pubescens seeds (EEPp) have been also reported. This study describes the effects of EEPp on T and B lymphocytes functions from healthy mice. Delayed Type Hypersensitivity (DTH), in vivo antibody production, T and B lymphocyte proliferation and NO production were determined. Mice treated orally for 7 days with EEPp had inhibited 58% of B cell antibody production (10(-3) mg kg(-1) b.wt.) and 33% of the DTH response (10(-4) mg kg(-1) b.wt.), also reducing tissue leukocyte infiltration. EEPp (10(-2) mg mL(-1)) also inhibited in vitro T (89%) and B (68%) lymphocytes proliferation and NO production (53%) by macrophage cell line J774. The immunosuppression here described for EEPp supports its potential therapeutic use to control exacerbated humoral and/or cellular immune response as in autoimmune and chronic inflammatory diseases.