Summary of the SAP-binding proteins.

Binding of SAP to the cytoplasmic tail of the cell surface receptors is indicated by a plus sign, and absence of binding to SAP is indicated by a minus sign. SAP binds to the phosphorylated (pY) cytoplasmic tails of SLAM, 2B4, Ly-9, and CD84 and only to the nonphosphorylated (Y) tail of SLAM. CD48 is the ligand for 2B4 (see “Discussion”). B, B lymphocyte; T, T lymphocyte; CD8, CD8⁺ lymphocyte; COOH, carboxy-terminus; DC, dendritic cell; Mφ, macrophage; NH2, amino-terminus; M, SAP-binding motif; –, N-linked carbohydrate side chain.