Inhibition of burn‐associated suppressor cell generation by glycyrrhizin through the induction of contrasuppressor T cells

The inhibitory effect of glycyrrhizin (GR), an anti‐inflammatory Chinese herbal drug extracted from licorice roots, on the generation of suppressor T cells in thermally injured mice (TI‐mice) was investigated. The burn‐associated suppressor T cell (BTs cell) activity was demonstrated in splenic mononuclear cells (SMNC) from mice 2 to 8 days after thermal injury when suppressor cell activity was assayed in a one‐way mixed lymphocyte reaction. However, when TI‐mice were treated with GR, SMNC harvested 6 days after thermal injury showed no suppressor cell activity. This activity of GR demonstrated a dose‐response effect, with a dose of 10 mg/kg exhibiting peak levels of the activity. Since GR had no direct inactivating activities against BTs cells in vitro, the inhibitory effect of SMNC, derived from TI‐mice treated with GR, on the activity of BTs cells was examined in the same mixed lymphocyte reaction system, and the results showed that the SMNC from GR‐treated mice 6 days after thermal injury counteracted the activity of BTs cells. The type of cell responsible for this inhibition of BTs cell activities was a CD3⁺, L3T4⁺, Vicia villosa lectin‐adherent T cell with the same phenotypic properties previously exhibited by contrasuppressor cells. These results suggest that GR may regulate the generation of BTs cells through the induction of contrasuppressor cells. Since there are many reports describing septic infections due to the appearance of BTs cells in postburn patients, it may be possible to apply GR or blood preparations containing contrasuppressor cell populations induced by GR in healthy volunteers into immunosuppressed burn patients to avoid infections.