G protein-coupled receptors (GPCRs) have been found to play important roles in the immune system. Innate and adaptive immune responses depend on the coordinated migration of immune cells between and within lymphoid organs and peripheral tissues. Inflammatory cells, including lymphocytes, monocytes, neutrophils, and dendritic cells, express numerous GPCRs that recognize the classical chemoattractants, chemokines, as well as a broad-spectrum of additional molecules, such as peptides, lipids, nucleotides, and extracellular matrix fragments, that can also regulate immune cell migration. In addition to chemoattractant receptors, immune cells also express many other GPCRs that regulate different aspects of an immune response including immune cell differentiation and maturation, inflammatory gene transcription, superoxide generation, and phagocytosis. R&D Systems offers a wide variety of research tools for investigating GPCRs including antibodies for GPCR detection and Tocris brand small molecules for modulating GPCR signaling.