LILRA4 (also known as ILT7 and CD85g) encodes a preprotein of 499 amino acids that gives rise to a surface receptor with four extracellular immunoglobulin domains, a transmembrane domain, and a short intracellular tail. The human LILR family of immunoreceptors is found on NK cells, T cells, monocytes, B cells, and dendritic cells. LILRA4 is a negative regulatory receptor that is found on resting pDCs and strongly downregulated after viral or bacterial stimulation. LILRA4 protein directly binds to and can be activated by bone marrow stromal cell antigen 2 (BST2; CD317) protein, the expression of which is found on cells preexposed to IFN or on the surface of human cancer cells. The interaction between ILT7 and BST2 functions to assure an appropriate TLR response by pDCs during viral infection and likely participates in pDC-tumor crosstalk.
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