Th1 cells, or T helper 1 cells, are a type of immune cell that play a crucial role in the body's defense against infections. They are a subset of CD4+ T cells and are primarily involved in activating macrophages and promoting the immune response against intracellular pathogens, such as viruses and certain bacteria. These cells produce specific signaling molecules called cytokines, particularly interferon-gamma (IFN-γ), which helps enhance the ability of other immune cells to eliminate infections. Th1 cells are essential for developing a strong immune response and are important in the context of various diseases, including autoimmune disorders and chronic infections.