T-helper 1 (Th1) cells are a type of immune cell that play a crucial role in the body's defense against infections, particularly those caused by viruses and certain bacteria. They are a subset of T-cells, which are essential for the adaptive immune response. Th1 cells help activate other immune cells, such as macrophages and cytotoxic T-cells, to effectively eliminate pathogens. Th1 cells produce specific signaling molecules called cytokines, with interferon-gamma being one of the most important. These cytokines enhance the immune response by promoting inflammation and increasing the ability of immune cells to destroy infected cells. This makes Th1 cells vital for maintaining a strong immune defense.