The cells of the immune system that provide protection from disease move about the body in the:

The cells of the immune system are primarily located and move through the fluids of the circulatory and lymphatic systems. This transportation system is essential for the immune cells, such as lymphocytes and macrophages, to effectively patrol the body for pathogens, respond to infections, and coordinate immune responses.

The lymphatic system specifically plays a crucial role in the immune function, as it helps in transporting lymph, which contains infection-fighting white blood cells. The circulatory system, on the other hand, facilitates the distribution of these immune cells throughout the body in the bloodstream, enabling them to reach areas where they are needed most.

In contrast, the airways and respiratory systems are primarily involved in gas exchange rather than in the movement of immune cells. The digestive tract serves its main function of processing food and absorbing nutrients, with some immune activity but not as a primary mode of transport for immune cells. The muscular system, while important for movement, does not play a direct role in the transport of immune cells or their function. Thus, the transportation and action of immune system cells are accurately described by their movement through the circulatory and lymphatic systems.