It affects Th1 responses, but data are conflicting: in mice infected with TB, metformin treatment promotes the expansion of Mtb-specific IFN-γ secreting T cells in the lungs (Singhal et al., 2014), whereas in human THP-1 cells (not infected with Mtb) metformin suppressed the production of Th1-related cytokines (Chen et al., 2018). The gene discussed is IFNG; the disease is tuberculosis.