Impact of Lithium on the Immune System: An Investigation of T-Cell Subpopulations and Cytokine Responses in Rats

The aim of this study was to investigate the dose-dependent adverse effects of long-term dietary lithium administration on specific aspects of the defense system in rats. Additionally, the study aimed to explore the inflammatory activities of lithium beyond its recognized anti-inflammatory properties. Forty Wistar Albino rats were involved, which were randomly allocated into the control and four treatment groups. The control group received standard rat feed, and the experimental groups’ diet was added 1 g/kg, 1.4 g/kg, 1.8 g/kg, and 2.2 g/kg lithium bicarbonate, respectively. CD4+, CD8+, and CD161 + cells were assessed by flow cytometry. TNF-α, IFN-γ, IL-1β, and IL-2 and IL-4, IL-6, and IL-10 levels were measured. The proportion of CD4 + cells and the CD4+/CD8 + ratio (P = 0.005 and P = 0.038, respectively) were reduced with the highest dose of lithium compared to the control group. The data regarding pro-inflammatory cytokines showed a dose-dependent increase in serum TNF-α and IFN-γ levels (P = 0.023 and P = 0.001, respectively). On the other hand, serum IL-1β and IL-2 levels were decreased in a dose-dependent manner (P = 0. 001 and P = 0. 001, respectively). As for anti-inflammatory cytokines, a dose-dependent decrease was determined in serum IL-4 level (P = 0.002), while no significant changes were noted in IL-6 and IL-10 levels (P = 0.507 and P = 0.732, respectively). In conclusion, lithium adversely impacted the cellular defense system. Furthermore, apart from its anti-inflammatory properties, lithium exhibited cytokine-mediated inflammatory activities. Therefore, lithium’s potential adverse effects on the immune system should be considered in immunodeficient patients and those with an inflammatory status treated with high doses of lithium.