Tea tree oil inhalations modify immunity in mice

Abstract

Tea tree oil (TTO) is well known as an anti-microbial and immunomodulatory agent and the latter property was examined in this study. Male, C57BI10 x CBA/H (F1), mice were exposed to TTO vapour three times a day, for one week. During this period, half of the mice also received naltrexone (endogenous opioid receptor antagonist) in their drinking water. A day before the end of the TTO inhalation treatment a number of the mice were intra-peritoneally injected with Zymosan or PBS. Spleens and peritoneal exudates were collected 24 h after the injections. Cultured splenocytes were used in in vitro proliferation assays with PHA, and LPS mitogens and peritoneal leukocytes (PTLs) were used for cytofluorimetric ROS level measurement. The results obtained confirmed the anti-inflammatory properties of TTO, expressed as an inhibition of the increase in the PTL number stimulated by Zymosan. This effect was reversed by naltrexone, suggesting that TTO acts via the endogenous opioid system. TTO also stopped the proliferation of splenocytes in response to mitogens and the activity of PTLs was equivalent to that seen in the control (without inflammation) groups.