Human Interferon-γ (IFN-γ) is a type II interferon cytokine that plays a central role in cell-mediated immunity and regulation of antimicrobial and inflammatory responses in humans (Homo sapiens). IFN-γ is produced primarily by activated T helper 1 (Th1) cells, cytotoxic T lymphocytes, and natural killer (NK) cells following stimulation by intracellular pathogens or immune signaling molecules such as IL-12 and IL-18. Human IFN-γ binds to the interferon-γ receptor (IFNGR1/IFNGR2) expressed on many immune and non-immune cells, activating intracellular signaling through the JAK–STAT pathway, particularly STAT1, which induces expression of numerous interferon-stimulated genes involved in antigen presentation, macrophage activation, and antimicrobial defense. IFN-γ is critical for activation of macrophages, enhancement of MHC class I and II expression, and control of intracellular pathogens, especially mycobacteria, viruses, and certain parasites. In human health, IFN-γ is essential for immunity against diseases such as tuberculosis and viral infections, and defects in IFN-γ signaling can lead to increased susceptibility to mycobacterial disease. Human IFN-γ is also widely studied and used in clinical diagnostics and immunotherapy, including IFN-γ release assays (IGRAs) for detection of Mycobacterium tuberculosis infection and therapeutic use of recombinant IFN-γ in certain immune deficiency and infectious disease conditions.