Effects of yellow brain culinary-medicinal mushroom, Tremella mesenterica Ritz.:Fr. (Higher basidiomycetes), on immune function in normal and type 1 diabetic rats

Diabetes mellitus (DM) is characterized by systemic low-grade inflammation and altered immunity. The fruiting bodies (FB) of Tremella mesenterica have been demonstrated to have anti-hyperglycemic and immunomodulatory activities. It is unclear whether submerged culture yeast-like cells (CC) of T. mesenterica have the same immune effects as FB. Here, we compared the immune effects of T. mesenterica FB and CC on immunocyte function. Male Wistar rats were intravenously injected with saline (normal rats) or streptozotocin (50 mg/kg, DM rats) and orally treated with placebo, FB, or CC (1 g/kg/day) for 2 weeks. Peripheral blood leukocytes and splenocytes were collected. In normal rats, FB and CC ingestion significantly decreased T-suppressor leukocyte numbers and interferon (IFN)-γ production in leukocytes (p < 0.05). In addition, CC treatment significantly decreased mitogen-stimulated tumor necrosis factor (TNF)-α and interleukin (IL)-6 production in leukocytes as well as the numbers of total and B splenocytes. In DM rats, FB significantly alleviated the diabetes-induced decreases in plasma TNF-α levels, T-helper splenocyte numbers, and IL-6 production in T leukocytes, and CC significantly attenuated the decreases in plasma TNF-α, IFN-γ, and IL-6 levels, as well as the increase in IL-6 production in T splenocytes induced by diabetes. Moreover, CC significantly decreased the numbers of T-helper leukocytes and B splenocytes as well as the production of TNF-α by splenocytes and IL-4 by leukocytes in DM rats. In conclusion, our results suggest that T. mesenterica FB and CC may decrease peripheral cell-mediated immunity in normal rats. However, in diabetic rats, FB may increase peripheral cell-mediated immunity, and CC may decrease pro-inflammatory and Th1 cytokine production.