T helper 1 (Th1) cells are a type of immune cell that play a crucial role in the body's defense against infections. They are a subset of T cells, which are white blood cells involved in the immune response. Th1 cells primarily help activate macrophages and cytotoxic T cells, enhancing their ability to eliminate pathogens, especially intracellular ones like viruses and some bacteria. Th1 cells produce specific signaling molecules called cytokines, such as interferon-gamma (IFN-γ), which further stimulate the immune response. This makes them essential for fighting off infections and for the development of certain autoimmune diseases. Their balanced activity is vital for maintaining overall immune health.