The effect of the immunomodulator RU 41,740 (biostim) on the specific and nonspecific immunosuppression induced by thermal injury or protein deprivation.

We studied the effect of RU 41,740 (biostim), a primary macrophage stimulator, in the following two immunosuppressive conditions in rats: (1) a 30% full-thickness burn that leads to significant decreases in cell-mediated (delayed-type hypersensitivity [DTH]), humoral (anti-tetanus toxoid antibody production), and nonspecific immunity (Staphylococcus aureus 502a skin abscess) and (2) protein malnutrition using a 2% protein diet for eight weeks. Biostim administered by gastric intubation at dosages of 10 and 50 mg/kg of body weight for five days following thermal trauma did not prevent the DTH suppression induced by the thermal injury, but resulted in a significant dose-related increase in the amount of anti-tetanus toxoid antibody produced. In the malnourished rats given biostim at dosages of 10 and 50 mg/kg of body weight for seven days, there was a significant dose-related increase in the DTH response in the presence of continued protein depletion in these animals, with a modest but significant reduction in the S aureus 502a skin abscess at three days. Antibody production was not affected with this model. Biostim partially overcomes the suppression in humoral immunity following thermal injury, but not cell-mediated or nonspecific immunity. On the other hand, biostim augments both the cell-mediated and nonspecific immune suppression induced by prolonged protein deprivation but does not affect humoral immunity.