The primary function of the lymphatic system in immunity is to transport lymph, a fluid containing white blood cells, throughout the body. This system plays a crucial role in the body's defense against infections by facilitating the circulation of immune cells, such as lymphocytes, which are essential for identifying and combating pathogens. The lymphatic system also filters foreign substances through lymph nodes, where immune responses can be triggered. Additionally, it aids in the removal of waste products and excess fluid from tissues. Overall, a well-functioning lymphatic system is vital for maintaining immune health and overall homeostasis.