The tracking beacons used by the Imperialists to track the Rebel fleet through hyperspace are similar to chemokines in our immune system. Chemokines are chemical messengers that direct cells of the immune system where to go.
Chemokines are a family of proteins that act as chemical messengers to direct cells of the immune system from the blood into the tissue and vice versa, so that cells are directed to where they are needed. The process of inducing cell movement is called chemotaxis, with cells following an increasingly strong signal directing them towards the site at which they are needed.
The chemokines are highly specific for individual cell types, ensuring that the correct cells arrive at the right time during the immune response. Chemokines can also be grouped as inflammatory or homeostatic, meaning that they try to maintain immune balance. Inflammatory chemokines are released by cells during infection or injury, whereas homeostatic chemokines are produced all the time, helping to direct immune cells to the lymph nodes.