The protective immune response is dependent on the continuous circulation of T cells in search of foreign invaders. As part of this process, T cells must exit lymphoid organs and traffic into the lymph and blood. This important event is regulated by the binding of sphingosine 1-phosphate receptor 1 (S1PR1) to its ligand, sphingosine 1-phosphate (S1P). Upon binding, S1P is internalized along with its receptor through clathrin-mediated endocytosis. Receptor internalization is typically associated with signal termination. However, in non-hematopoietic cells stimulated by artificial agonists, there is evidence that S1PR1 can continue signaling from endosomes. Thus, for my independent research project, my objective was to investigate the signaling behavior of S1PR1 following internalization. Understanding the nature of S1PR1, as it relates to T cell migration, is crucial to learning what regulates proper immune function.