Thus, we suspect that the mTOR pathway might be upregulated by metformin treatment, even though the increase in mTOR phosphorylation was undetectable by flow cytometry using our conditions. while that of T cells did not. The proportions of V1+ and V2+ T cells increased, suggesting that activated cells were selectively expanded. However, these T cells expressed inhibitory receptors and had severe defects in cytokine production, suggesting that they were in a state of exhaustion. Metformin was unable to rescue the cells from exhaustion at this stage. Depletion of T cells with antibody treatment did not affect the reduction of parasitemia in metformin-treated mice, suggesting that the effect of metformin on the reduction of parasitemia was independent of T cells. parasites and is one of the most serious infectious diseases in the world. In endemic areas of tropical and subtropical countries, more than two million people suffer from malaria and ~445,000 people died from the disease in 2016, according to a World Health Organization (WHO) malaria report (1). Strains of resistant to drugs, including artemisinin, are emerging and there is an immediate need for the development of effective vaccines. However, repeated infections and a prolonged amount of time are required for people living in endemic countries to gain natural resistance to malaria, and the memory response to antigens appears to be lost in the absence of repeated infections (2, 3). It is important to define and understand the underlying mechanisms involved in the formation and maintenance of adaptive immune responses against infections to devise novel strategies for developing a malaria vaccine and to improve its effectiveness. While antibody and CD4+ T-cell responses are the primary effector mechanisms of protective immunity against blood-stage infection with parasites, several studies indicate that T cells also participate in the immune response. Infection IL-20R2 of humans with is associated with increased numbers of polyclonal T cells in the peripheral blood (4, 5). In particular, T cells expressing V9 and V2 are activated by the recognition of phosphorylated molecules of merozoites INCB39110 (Itacitinib) in a cellCcell contact-dependent manner, suggesting a protective role of T cells against parasites (8). Another study showed that the reduction of V2+ T cells, which respond to infection was associated with a reduced likelihood of symptoms upon subsequent infection with and infection (15, 16). Depletion of T cells using a monoclonal antibody (mAb) resulted in persistent infection with the non-lethal XAT strain, which is normally eliminated by the protective immune response (17). In this model of XAT infection, T cells expressed both CD40 ligand and interferon (IFN)- during the early phase of infection and enhanced the function of dendritic cells, thereby promoting protective immunity against parasites (15). Recent studies revealed metabolic changes in T cells after their activation and during the generation of memory. Activated T cells switch the main pathway of adenosine triphosphate (ATP) generation from INCB39110 (Itacitinib) oxidative phosphorylation to glycolysis, which enables the generation of substrates required for synthesizing macromolecules such as nucleotides, proteins, and lipids, which promote rapid proliferation and effector function (18, 19). Metabolism in T cells is regulated by T-cell receptor (TCR) and cytokine-receptor signaling pathways involving Myc, hypoxia-inducible factor (HIF)-1a, and mammalian target of rapamycin (mTOR), which are crucial for regulating T cell activation and differentiation, and increasing or decreasing the metabolic output of cells in response to ligand stimulation (19). Adenosine monophosphate (AMP)-activated protein kinase (AMPK) senses the intracellular AMP/ATP ratio and induces a metabolic switch to promote ATP conservation by enhancing glucose uptake, fatty acid oxidation, mitochondrial biogenesis, and oxidative metabolism. Metformin is widely used as an oral agent to treat patients with type-2 diabetes (20). Metformin is a derivative of the biguanide drugs, which were originally discovered as an antimalarial agent (21, 22). The antimalarial activities of the biguanide drugs were initially attributed to inhibition of the dihydrofolate reductase INCB39110 (Itacitinib) enzyme of the parasite,.