Eugenol modulation of the immune response in mice.

The effect of eugenol on selected parameters of the immune response of C57BL/6 mice was studied. In a dose-response study, eugenol at high doses completely inhibited the plaque-forming cell responses of splenocytes to the T-dependent antigen (sheep erythrocytes) both in vitro and in vivo. In vitro, at concentrations higher than 1.0 mM, eugenol was found to be cytotoxic. In vivo, however, at very low doses there appeared to be a suppression of the plaque-forming cell response to sheep erythrocytes, reaching maximal suppression at 0.1 mumol eugenol/kg mouse body weight. This was followed by enhancement of the response, peaking at 0.25 mumol eugenol/kg mouse body weight. These changes correlated fairly well with body weight changes. Thymic weights appeared to remain unchanged for all doses except the 1.0 mumol eugenol/kg body weight, which was significantly (p less than 0.05) higher than the rest of the groups. Natural killer activity at all effector:target ratios (100:1, 50:1, 25:1) was significantly (p less than 0.05) enhanced at both 0.25 and 2.5 mumol eugenol/kg body weight. Overall, eugenol seems to have dose-dependent suppressive and enhancing effects on the immune response. These effects represent an atypical multiphasic response in which an inversed dose-response relationship is observed.