Schematic representation of the CD300 receptors in human (A) and mouse (B). The extracellular domain of the ITIM-containing receptors is colored in turquoise, and that of the non–ITIM-containing receptors is colored in green. The extracellular domain of CD300g is colored in brown. The signaling motifs of each receptor are indicated, and the interaction with phosphatases, adaptor molecules, and kinases is shown. It is important to note that some associations of CD300-activating molecules with adaptor proteins have been demonstrated only in cells transfected with complementary DNAs encoding the corresponding adaptor proteins. The question marks indicate that the signaling pathway is currently unknown. The nomenclature for the mouse receptors follows the nomenclature shown in Figure 1.