Inhibitory and activating receptors involved in immune surveillance by human NK and myeloid cells.

We review the structure, cellular distribution, ligand specificity, and function of two emerging types of receptors involved in natural killer (NK) and myeloid cell recognition of other cells: ILT/LIR/MIR and 2B4 receptors. ILT/LIR/MIR receptors are differentially expressed on lymphoid and myeloid cells and two of them, ILT2 and ILT4, recognize HLA class I molecules. Whereas some receptors inhibit, others induce cell activation. 2B4 is broadly expressed on leukocytes, binds CD48, and mediates non-MHC-restricted cytotoxicity by NK cells.