Abstract
An immunosuppressive compound found in the fruiting body of Suillus bovinus has been identified as suillin. DNA synthesis rates of murine lymphocytes were superiorly suppressed by suillin in the mitogenic stimulation by lipopolysaccharide than in that by concanavalin A. Therefore, suillin is suggested to have an immunosuppressive activity which preferentially perturbs B-lymphocyte function.