Altered ex vivo cytokine production in zinc-deficient, pair-fed and marginally zinc-deficient growing rats is independent of serum corticosterone concentrations.

The objective of the present study was to examine the effects of dietary Zn deficiency on the ex vivo cytokine production (IL-2, interferon-gamma (IFN-gamma), IL-6 and IL-10) of isolated thymocytes and splenocytes after mitogenic stimulation with concavalin A and to explore the role of corticosterone in this regulation. Weanling rats were assigned to one of four dietary treatments for 3 weeks: Zn-deficient (< 1mg Zn/kg diet, ad libitum), pair-fed (30 mg Zn/kg diet, limited to amount of feed as consumed by the Zn-deficient group), marginally Zn-deficient (10 mg Zn/kg diet, ad libitum) and control (30 mg Zn/kg diet, ad libitum). Thymocytes and splenocytes were isolated for cytokine stimulation and determination of T-cell phenotypes. Serum corticosterone concentrations were determined by ELISA. The Zn-deficient and pair-fed groups had 14-fold higher serum corticosterone concentrations compared with the marginally Zn-deficient and control groups (P<0.0001). The proportions of thymocyte subsets were not altered in the Zn-deficient, pair-fed or marginally Zn-deficient groups; however, thymocyte IL-2 and IL-6 production in these groups was 33-54% lower compared with the control group (P<0.05). The Zn-deficient group had an 18-28% lower proportion of new T-cells (TCRalphabeta+CD90+), but no difference in the proportion of new T-cells that were cytotoxic or helper. The Zn-deficient group had a 49-62% lower production of Th1 cytokines (IL-2), but no difference in the production of Th2 cytokines (IL-6, IL-10) by stimulated splenocytes compared with the pair-fed, marginally Zn-deficient and control groups (P<0.01). These results indicate that Zn status is associated with altered cytokine production, while in vivo corticosterone concentrations are not associated with ex vivo cytokine production.