Chemokines, also known as chemotactic cytokines, are a specific type of cytokines that guide directional cell movement in the activation of immune responses. They are classified into four groups depending on the spacing of their first two cysteine residues: CXC, CC, CX3C and C. All of these proteins transmit cell signals through chemokine receptors, which are G protein‐coupled receptors selectively present on the surfaces of their target cells.