Human IgG receptors. Schematic representation of human IgG receptors at the cell membrane (gray bar) and their association or not to the FcRγ-chain dimer (black). Green boxes represent ITAMs; and the white box, the ITIM. Binding of a human IgG subclass is indicated in bold (high affinity), plain (low affinity), or between parentheses (very low affinity). - indicates no binding.